ORACLE TO SYBASE ASE
MIGRATION GUIDE
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3
Table of Contents 1 Introduction ...... 4 1.1 Intended Audience ...... 4 1.2 What You Should Already Know ...... 4 1.3 About Sybase ASE ...... 4 1.4 Oracle systems targeted by this Guide ...... 4 1.5 Oracle products vs. Sybase products ...... 4 1.6 Oracle / Sybase database versions covered ...... 5 1.7 Sybase ASE documents and references ...... 5 2 How to use this Migration Guide...... 6 2.1 Migration process outline ...... 6 2.2 Success factors ...... 6 2.3 Not covered by this guide: Project aspects ...... 7 2.4 Not covered by this guide: Sybase ASE-specific tuning ...... 7 3 Pre-migration complexity assessment ...... 8 3.1 Oracle checklist: datatypes ...... 8 3.2 Oracle checklist: category "Simple Conversion" ...... 8 3.3 Oracle checklist: category "Partial Rewrite" ...... 12 3.4 Oracle checklist: category "Major Rewrite" ...... 15 4 Database Schema Migration ...... 17 4.1 Obtaining the Oracle schema definition ...... 17 4.1.1 Using existing DDL scripts ...... 17 4.1.2 Reverse-engineering the existing schema ...... 17 4.2 Using Sybase PowerDesigner for database schema migration ...... 18 4.2.1 PowerDesigner schema conversion steps ...... 18 4.3 Reverse-engineering the Oracle schema without Sybase PowerDesigner ...... 18 4.4 Special cases in schema migration ...... 18 4.5 Mapping the Oracle schema to Sybase ASE databases ...... 19 4.6 Schema-related Oracle-Sybase terminology ...... 20 4.7 Mapping Oracle Datatypes to Sybase ASE ...... 21 4.7.1 Chained Oracle data rows ...... 23 4.8 Search for Sybase ASE reserved words and keywords in Oracle ...... 23 4.9 Choosing a lock scheme for Sybase ASE tables ...... 24 4.10 The Oracle DUAL Table ...... 24 5 Migrating server-level aspects ...... 25 5.1 Character set ...... 25 5.2 Database server case sensitivity ('sort order') ...... 25 5.3 Server configuration parameters ...... 26 5.4 Storage ...... 26 5.5 Migrating the User Logins ...... 26 5.5.1 User passwords ...... 27 5.6 Permissions ...... 27 6 Data Migration ...... 28 6.1 Unload Oracle data into ASCII files; load into ASE with "bcp" utility ...... 29 6.1.1 Loading into ASE with "bcp" ...... 29 6.1.2 Unloading from Oracle: FACT (3rd-party tool) ...... 29 6.1.3 Unloading from Oracle: Roll-your-own PL/SQL utility to export Oracle data...... 30 6.1.4 Unloading from Oracle: use Oracle SQL Developer ...... 30 6.2 Use Sybase's Enterprise Connect Data Access (ECDA) Option for Oracle ...... 30 6.2.1 ECDA Example ...... 30 6.3 Use Sybase Replication Server Heterogeneous Edition (RSHE) for Oracle ...... 30 6.3.1 Minimal migration downtime with Replication ...... 30 6.3.2 Initial materialization for the replication setup ...... 31 6.3.3 Other considerations ...... 31
Introduction 2
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3
6.4 Use a 3rd-party ETL tool that supports both Oracle and Sybase ASE ...... 32 6.5 Oracle datatypes requiring special attention for migration ...... 32 7 Migrating PL/SQL to Transact-SQL ...... 33 7.1 Locations of PL/SQL code ...... 33 7.2 3rd-party tools for PL/SQL migration to T-SQL ...... 33 8 Transactions and Locking, Oracle vs. Sybase ...... 35 8.1 Oracle MVCC vs. Sybase locking ...... 35 8.2 Transaction-related migration issues ...... 35 8.3 Using ASE implicit/chained transaction mode ...... 36 8.3.1 Transactional DDL ...... 36 8.3.2 Transaction processing in stored procedures ...... 36 8.4 Using ASE explicit/unchained transaction mode ...... 36 8.5 Using ASE transactional concurrency enhancements ...... 36 8.6 Other transactional aspects ...... 37 9 Miscellaneous migration aspects ...... 39 9.1 Cursors ...... 39 9.2 Sequences ...... 39 9.3 Error/Exception handling ...... 41 9.4 Outer join limitations ...... 41 9.5 Migrating JDBC/ODBC/… Applications ...... 42 9.5.1 JDBC ...... 42 9.6 Oracle Forms ...... 42 10 DBA Tasks Cross-Reference ...... 43 11 Oracle-to-Sybase Migration Cross-Reference ...... 47 11.1 Oracle-to-Sybase ASE migration: category "Simple Conversion" ...... 47 11.2 Oracle-to-Sybase ASE migration: category "Partial Rewrite" ...... 56 11.3 Oracle-to-Sybase ASE migration: category "Major Rewrite" ...... 64
Revision history: Rev.1.0: September 2011: initial version Rev.1.1: November 2011: expanded the topic on case-sensitivity; various other additions Rev.1.2: October 2012: many extensions to chapters 3 & 11; added example of sequence equivalent in ASE Rev.1.3: December 2012: replaced PowerDesigner and ECDA examples by pointers to a separate document
© 2011-2012 Sybase, Inc. Sybase, Transact-SQL, Adaptive Server Enterprise and Replication Server are registered trademarks of Sybase, Inc. Other product or brand names may be (registered) trademarks of their respective owners.
Introduction 3
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3
1 INTRODUCTION This Migration Guide aims to provide guidance and assistance with the migration process from an Oracle database to Sybase ASE (Adaptive Server Enterprise). By "migration" we mean the process of changing a client-server application currently using the Oracle database as its RDBMS, such that it uses the Sybase ASE database instead. This Migration Guide has as its primary focus to migrate functionality from Oracle to Sybase ASE. Performance-related aspects of Sybase ASE are not covered (also see section 2.4).
1.1 Intended Audience This Migration Guide is intended for anyone involved in migrating an Oracle database to Sybase Adaptive Server Enterprise (ASE).
1.2 What You Should Already Know The reader is expected to be familiar with relational database concepts, and with Oracle in particular. In addition, introductory knowledge of the Sybase ASE RDBMS is required. For a database migration to be successful, there should be a detailed understanding of the current Oracle-based system, including its high- and low-level architecture, as well as the interaction between the client application and the Oracle database.
1.3 About Sybase ASE Sybase ASE is the database that powers Wall Street. ASE has been delivering rock-solid reliability and top-level performance for the past 25 years. Sybase ASE has a lower total cost of ownership than Oracle, and delivers better performance on the same hardware. Sybase ASE is ready to be the database in any application that runs on Oracle today.
1.4 Oracle systems targeted by this Guide This Migration Guide can be used for migrations of any type of Oracle-based system. While it does not focus on a specific type of application, workload or system design, the majority of Oracle-based migration candidate systems are expected to be transactional systems. This Migration Guide specifically does not aim at migrating SAP Business Suite installations currently running on Oracle, to run on Sybase ASE instead. Since such migrations are covered by product and service offerings by SAP, interested customers should contact SAP directly.
1.5 Oracle products vs. Sybase products Both Oracle and Sybase provide a range of database-related products. The following list illustrates how the main high- level Oracle products compared to Sybase products. While this list is deliberately kept brief, it provides some basic guidance on how Oracle and Sybase can be aligned. The focus of this Migration Guide is on migration from Oracle Database Server to Sybase ASE. These are usually expected to be OLTP-oriented systems, though this is not required. Oracle Sybase Oracle Database Server Sybase ASE (Adaptive Server Enterprise) Oracle OLAP and DW Sybase IQ Oracle RAC Sybase ASE Cluster Edition Oracle Times Ten Sybase ASE In-Memory Database Oracle Streams Sybase Replication Server
Introduction 4
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3
1.6 Oracle / Sybase database versions covered This document pertains to Oracle versions 9i, 10g and 11g. The migration target is assumed to be Sybase ASE version 15.7 (or later). Migration to earlier ASE versions is not recommended and not covered by this Migration Guide. If not otherwise specified all references to "ASE" or "Adaptive Server" are considered references to "Sybase Adaptive Server Enterprise".
1.7 Sybase ASE documents and references For more detailed information about Sybase ASE , see http://www.sybase.com/ase for general documents and whitepapers. See http://www.sybase.com/support/techdocs/migration for resources specifically focused at (different types of) migrations. These include the document you are currently reading, as well as “Migrating an Oracle Database to SAP Sybase ASE with PowerDesigner and ECDA (A Step-By-Step Practical Guide)” . For ASE documentation and product manuals, see http://infocenter.sybase.com . Specifically, the following ASE documents are relevant: Transact SQL User's Guide Reference Manual System Administration Guide Utility Guide Performance and Tuning Guide
In addition, Sybase provides technical training for ASE. For details on courses and availability, see http://www.sybase.com/education.
Introduction 5
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3
2 HOW TO USE THIS MIGRATION GUIDE The focus of this Migration Guide is on the database-specific technical aspects of an Oracle to Sybase database migration project. In particular, it aims to help identify and assess the complexity of the migration when scoping out a migration project, so as to avoid overlooking or underestimating potentially difficult aspects of the system to be migrated. In addition, it helps establish a migration approach by providing and suggesting technical options for various aspects of the migration process.
2.1 Migration process outline This Migration Guide recommends a phased approach towards migrating from Oracle to Sybase ASE. The following phases can be identified, in order of importance and priority: 1. Before starting the actual migration project, assess the complexity of the migration using the checklist in chapter 3. This activity involves identifying specific Oracle features used in the current system which may not have a direct Sybase equivalent. It is strongly recommended to pay sufficient attention to this activity, as this helps to avoid overlooking or underestimating the most difficult parts of a migration.
2. Migrating the database schema is the necessary first step of an actual migration (described in chapter 4). This Migration Guide recommends using Sybase PowerDesigner to reverse-engineer the Oracle schema and convert it to the Sybase ASE equivalent.
3. Migrating server-level aspects such as users (described in chapter 5).
4. Migrating the data itself (described in chapter 6). The approach chosen to perform the data migration is usually driven by the maximum tolerable downtime allowed for the application. It is recommended to consider using 3rd-party tools for extracting data from Oracle. If minimal application downtime is crucial, consider Sybase Replication Server to reduce this downtime to minutes rather than hours.
5. Migrating Oracle PL/SQL code to Sybase Transact-SQL (also see chapter 7). This needs to be performed both for SQL located in the database (i.e. stored procedures, triggers, SQL functions) as well as for SQL code in client applications. This step tends to be the most complex part of a migration. To assist with this migration step, chapter 11 contains cross-reference between Oracle features and their Sybase ASE equivalent, in the three categories "Simple conversion possible", "Partial rewrite required" and "Major rewrite required". This cross-reference is an extended version of the Oracle checklist in chapter 3.
6. Migration of vendor-specific infrastructural components, such as JDBC drivers (see section 9.5).
7. Convert the maintenance, administration and monitoring tasks. Since these aspects are highly specific for each database brand, "migration" would be a misnomer. Chapter 10 contains a cross-reference of some common DBA aspects. This is however not sufficient for performing a migration, and specific DBA skills, both for Oracle and Sybase, will be required.
8. The primary focus of this Migration Guide is to help achieve functional equivalence of the Oracle system after being migrated to Sybase ASE. As a next step, Sybase ASE-specific optimization and tuning will likely be required in order to achieve desired performance levels. Sybase ASE-specific tuning is not covered by this Migration Guide; see section 2.4.
2.2 Success factors Database migrations can be complex, and costly migration failures need to be avoided. The following success factors apply to any Oracle-to-Sybase database migration project:
How to use this Migration Guide 6
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3
Domain knowledge of the business application(s), system and environment. It is essential to have a full and complete understanding of all applications that access the Oracle database being migrated. This includes the client applications that connect to the Oracle database directly, but also applications that indirectly access the database, for example through an application server. For all these applications, it needs to be understood which data the application accesses in the database, and how it modifies such data. Any SQL code submitted to the database by the application must be identified, as well as how such SQL code can be changed. Availability of sufficient Oracle expertise to analyze all aspects of the database is an absolute requirement. A key activity is to identify which specific Oracle features are used (as per the checklists in chapter 3), especially those which do not have a direct Sybase equivalent. Full access to all Oracle PL/SQL code being used, both in the database and in all client applications. As a minimum, sufficient understanding of Sybase ASE in order to create a functionally working migrated database system. At a later stage in the migration project, more specialized Sybase expertise will likely be needed for Sybase ASE-specific performance tuning and optimization. Having such expertise available at an early stage may be helpful. A comprehensive testing process and production-like environment for validating the migration approach and the affected software applications against the migrated Sybase database. For best results, it is highly recommended to use a copy of production data (as close as possible) as well as hardware which is similar in size to production.
2.3 Not covered by this guide: Project aspects This Migration Guide does not prescribe or suggest how to organize a migration project in terms of preparation, setting up testing procedures, validating the migrated components, etc. These aspects of a migration project are left to requirements, standards, best practices and preferences of the organization undertaking the emigration effort. Please note that the absence of specific recommendations for testing and validation of migrated components does not mean that such activities should not be performed. On the contrary, these activities are essential, and it is recommended to follow generally accepted best practices with respect to software testing and validation.
2.4 Not covered by this guide: Sybase ASE-specific tuning The primary purpose of this Migration Guide is to assist in creating a functionally equivalent Sybase ASE-based system compared with the original Oracle-based system. The purpose of this Migration Guide is not to provide guidance for arriving at an optimally tuned Sybase ASE system; while Sybase ASE-specific tuning will likely be necessary as part of a migration project, this Migration Guide deliberately makes no attempt to cover such tuning aspects. Since ASE-specific tuning is considered to be mostly unrelated to any Oracle-specific aspects or considerations, the reader is referred to the Sybase ASE documentation for background and recommendations about Sybase ASE tuning., specifically the System Administration Guide and the Performance and Tuning manuals.
How to use this Migration Guide 7
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3
3 PRE-MIGRATION COMPLEXITY ASSESSMENT For a database migration project, it is crucial to have an accurate assessment of the complexity of the migration ahead of time. Here, "complexity" refers to how Oracle-specific features can be mapped to the feature set of Sybase ASE. Before starting the actual migration effort, the current Oracle system should be closely inspected and a list should be drawn up of all types of Oracle-specific features being used, and how many times these occur. For each feature used, it should be determined in which of the following three categories it falls: Simple conversion possible An Oracle feature or statement can be mapped and converted directly to a (nearly) identical Sybase ASE feature, requiring no syntax changes or only simple, local syntax changes only. Examples: most datatype mappings (Oracle VARCHAR2 Sybase VARCHAR); simple SELECT statements Partial rewrite required An Oracle feature or statement can be mapped to a partly equivalent Sybase ASE feature, requiring potentially significant syntax changes and possibly partial rewriting of algorithms. Example: Oracle sequences Sybase ASE identity columns Major rewrite required An Oracle feature or statement has no directly equivalent Sybase ASE feature, requiring rewriting or redesigning of algorithms or parts of applications. Example: Oracle Flashback; Oracle row-level triggers. Categorizing the Oracle features used by the system being migrated helps to identify the areas where most migration complexity is likely to occur. Before deciding to start the migration project, there should be a clear view of the number of occurrences of the features in the categories "Partial rewrite required" and "Major rewrite required" above, and of the effort to migrate these, especially those in the Major rewrite required" category. To assist with this complexity assessment, below are three checklists, corresponding to the categories above, listing a range of Oracle features. Note that additional Oracle features may occur in your system that are not in these checklists; these should be taken into account just as well. The checklists below list the Oracle features only very briefly. Chapter 11 contains extended versions of these checklists with the corresponding Sybase ASE equivalent for each Oracle feature.
3.1 Oracle checklist: datatypes Verify the datatypes used in the current Oracle application; see section 4.7. Also see: section 4.7.1 for considerations that apply when migrating data rows whose length exceed an Oracle disk block; section 6.5 for considerations that apply when migrating particular datatypes.
3.2 Oracle checklist: category "Simple Conversion"
#cases found Oracle checklist: category "Simple Conversion"
Connecting to an Oracle schema
The Oracle SQL*Plus “slash” character sends preceding PL/SQL text to the Oracle server.
Semicolon (as a statement delimiter in PL/SQL)
Pre-migration complexity assessment 8
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3
#cases found Oracle checklist: category "Simple Conversion"
The Oracle DUAL table
SET SAVEPOINT savepoint-name
Variable/Parameter declarations; naming syntax
Assign default value in variable declaration
Multiple variable declarations with a single DECLARE keyword
Declarations without DECLARE keyword in declaration section of stored procedures/functions
Variable assignment
Transferring table data into a variable
Constants
%TYPE denotes the datatype of a column in an existing table
Dynamic SQL (Execute-immediate)
Loops with LOOP/END LOOP
FOR loops
CURSOR loops
Oracle Outer join syntax
SET TRANSACTION READ WRITE
ALTER TABLE mytable TRUNCATE PARTITION partition_name
CREATE OR REPLACE PROCEDURE (or FUNCTION)
ALTER PROCEDURE (or FUNCTION)
CREATE PROCEDURE… IS…
Stored procedure execution with named parameters (param => value)
Stored procedure execution with positional parameters (:var)
Stored procedure execution
SQL Function declaration with DETERMINISTIC keyword
Execution of a SQL Function
DECLARE CURSOR cursor-name IS…
Oracle cursors
Pre-migration complexity assessment 9
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3
#cases found Oracle checklist: category "Simple Conversion"
Cursor Attribute %ISOPEN
Cursor Attributes %FOUND, %NOTFOUND
Cursor Attribute %ROWCOUNT
AFTER triggers (on statement level)
INSTEAD OF triggers (on views)
SQL%ROWCOUNT
BOOLEAN datatype (for PL/SQL variables only)
MERGE statement
Partitioned tables with composite partitioning
Performance-optimized native PL/SQL datatypes (for PL/SQL variables only)
BINARY_INTEGER BINARY_DOUBLE BINARY_FLOAT
IF-THEN-ELSE
Multiple statements in an IF-THEN-ELSE branch
Conditional test based on EXISTS subquery
String concatenation operator: ||
userenv('sessionid')
MOD(X,Y)
CEIL()
TRUNC(number)
SUBSTR()
SUBSTR() function with two parameters
LENGTH()
CHR()
REPLACE()
TO_CHAR(expression)
TO_CHAR(expression, datepart)
Pre-migration complexity assessment 10
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3
#cases found Oracle checklist: category "Simple Conversion"
TO_CHAR(expression, format-string)
TO_NUMBER(expression)
Date/time functions and calculations
SYSDATE, SYSTIMESTAMP
TRUNC(date/time [,unit])
LAST_DAY()
NVL() function
Inconsistent use of upper/lowercase for identifiers (Oracle is case-insenstive for identifiers)
Identifiers that are Sybase ASE reserved words (see section 4.8)
INSTR() function with two parameters
Derived tables (also known as "inline views") without correlation name
ALTER TABLE … SPLIT PARTITION… ALTER TABLE … MERGE PARTITIONS…
Quoted identifiers. Oracle allows using quoted identifiers by enclosing an identifier in double quotes.
Oracle hints
Pre-migration complexity assessment 11
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3
3.3 Oracle checklist: category "Partial Rewrite" For the Oracle features listed below, migration to partly equivalent Sybase ASE features is possible, although potentially significant syntax changes and possibly partial rewriting of algorithms may be required.
#cases found Oracle checklist: category "Partial Rewrite"
Database links
External tables
Sequences
Table-valued User-defined SQL Functions
Pipelined Table Functions
Synonyms
Comments on database objects
Bitmap indexes
Temporary tables
IS TABLE OF, AS VARRAY(n)OF
Nested tables
Object tables
%ROWTYPE
Define a PL/SQL record type by enumerating the fields with IS RECORD OF or TYPE…IS RECORD
Non-integer RETURN value in stored procedure
User-defined Packages
Overloaded stored procedures
PL/SQL Exception handling; defining exception handlers
SQLCODE, SQLERRM
RAISE_APPLICATION_ERROR
Column Encryption
LOB locators
Pre-migration complexity assessment 12
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3
#cases found Oracle checklist: category "Partial Rewrite"
Data compression
Retrieving data to the client in stored procedures using DBMS_OUTPUT package
DBMS_*, UTL_* package calls (excl. DBMS_OUTPUT)
SDO_* package calls
SQL*Loader (sqlldr)
Materialized Views
Global variables (in a PL/SQL package)
INTERSECT construct
MINUS construct
Specific SQL clauses AS OF CROSS IGNORE AS OF TIMESTAMP CUBE ITERATE CONNECT BY FOR NATURAL DIMENSION KEEP NULLS DIMENSION BY MAIN NULLS FIRST EXCLUDE MODEL NULLS LAST GROUPING SETS NAV ROLLUP INCLUDE NOCYCLE SIBLINGS MEASURES NOWAIT SINGLE RETURN ALL ROWS ON REFERENCE RETURN UPDATED ROWS ONLY LOCKED PARTITION BY RULES START WITH REFERENCE SAMPLE UNIQUE SYSTIMESTAMP SEED UNPIVOT SKIP WAIT
INITCAP( string-expression )
INSTR() function with three or four parameters
NVL2() function
DECODE() function
Primary key and foreign key with different datatypes, different precision/scale (for numeric datatypes) or different length (for character datatypes)
Cluster (as created with CREATE CLUSTER)
Pre-migration complexity assessment 13
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3
#cases found Oracle checklist: category "Partial Rewrite"
SQL functions where the last statement is not RETURN
Derived tables (also known as "inline views") using "with" syntax
UNIONs in cursors
PRAGMA directives
Autonomous transactions
ON DELETE CASCADE constraints
XMLTYPE (XML data type) XML functions extract(), existsnode(), xmlexists(), etc
ROWID
ROWNUM
Pre-migration complexity assessment 14
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3
3.4 Oracle checklist: category "Major Rewrite" For the Oracle features listed below, no direct equivalent is available in Sybase ASE. Consequently, rewriting or redesigning algorithms or parts of applications will be required.
#cases found Oracle checklist: category "Major Rewrite"
Oracle MVCC (Multi-Version Concurrency Control; "writers don‟t block readers, readers don't block writers") Relevant aspects: Applications or queries relying on non-blocking MVCC Long-running transactions DDL in transactions SET TRANSACTION READ ONLY SQL*Plus autocommit/commit-on-exit
SQL*Plus
BEFORE triggers
Triggers on row level (BEFORE and AFTER)
Multiple triggers for a DML type on a table
REF CURSOR
Regular Expressions; functions REGEXP_LIKE(), REGEXP_SUBSTR(), REGEXP_REPLACE(), REGEXP_INSTR()
Windowing queries (SELECT…OVER(…) …)
SQL function OUT/IN OUT parameters
Non-deterministic SQL Functions (functions whose result may be independent of the function input parameters)
SQL Aggregate Functions
BFILE datatype
Oracle Streams; Oracle Data Guard
Oracle RAC for high-availability
Pre-migration complexity assessment 15
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3
#cases found Oracle checklist: category "Major Rewrite"
Oracle Flashback
Oracle Snapshot Standby
Oracle SQL Plan Management
AWR (Automatic Workload Repository)
Oracle Advanced Queuing
Packages for PL/SQL web access OWA_CUSTOM, OWA_CX, OWA_OPT_LOCK, OWA_SEC, OWA_TEXT, OWA_UTIL
Oracle Forms
Pre-migration complexity assessment 16
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3
4 DATABASE SCHEMA MIGRATION The first step in migrating an Oracle database to Sybase ASE is to migrate the database schema. Here, "database schema" refers to the physical data model. In other words, to the definition of the database structure, specifically of the tables, columns, indexes, views, datatypes, etc., typically expressed in SQL DDL (Data Definition Language), for example as e.g. 'create table' statements. There is some potential for terminology clash around the term "schema": As a generic database concept, "schema" is the definition of the database structure as described above, regardless of which database user owns the object(s). In Oracle, a "schema" is an central concept. It is a collection of database objects (tables, views, stored procedures, triggers, etc) owned by a particular user. A decision will need to be made as to how to map an Oracle schema to an ASE schema; see section 4.5 for details. In Sybase ASE, a "schema" is usually understood to refer to the generic concept of database schema. NB: For completeness, ASE also has a command create schema authorization which creates a number of tables and views plus associated permission settings as a transactional unit. This command is however rarely used in ASE and it is not used or discussed further in this Migration Guide. For clarity, this Migration Guide will use "Oracle schema" when referring to the Oracle-specific interpretation of "schema". In all other cases, "schema" refers to the generic concept of "database schema" as above.
Please note: none of the methods describes in this chapter converts Oracle's PL/SQL code into Sybase's Transact- SQL, which is needed when converting stored procedures, triggers and SQL functions. 3rd-party tools which such capabilities exist; see section 7.2 for more information.
4.1 Obtaining the Oracle schema definition When migrating the database schema from Oracle to ASE, we first need to obtain the Oracle schema, and then convert this to a format and syntax that can be used in Sybase ASE. In principle there are two methods to obtain the Oracle schema: Use existing DDL scripts from which the Oracle schema was created in the past; typically, in well-organized environments, such scripts are kept in a source code repository under version control. Reverse-engineer the Oracle schema from the actual Oracle database.
4.1.1 Using existing DDL scripts If not using a tool to reverse engineer and migrate the schema, then using existing DDL scripts would be the ideal starting point, since no further work is required to obtain the Oracle schema. However, the question is whether it can be guaranteed that such scripts are up-to-date and identical to the actual Oracle database. It is not uncommon to see that changes to the database schema have been made without updating the DDL scripts in the repository. Clearly, basing oneself on incorrect DDL scripts will cause problems later in the migration process. When existing Oracle DDL scripts are available, the next step is to convert the datatypes to Sybase ASE. Section 4.7 describes the mapping from Oracle datatypes to Sybase ASE. In addition, some aspects of the Oracle schema require special attention; see section 4.4.
4.1.2 Reverse-engineering the existing schema The alternative to using existing scripts is to reverse-engineer the Oracle schema from the actual Oracle database. This is more work, and may require special tools, but it has the advantage that the generated DDL is correct. When existing scripts cannot be used or relied upon, this Migration Guide recommends using Sybase PowerDesigner for reverse-engineering and migrating the database schema. Since PowerDesigner can reverse-engineer all tables, indexes,
Database Schema Migration 17
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3 etc, and automatically convert the Oracle datatypes into their ASE equivalent, this is the fastest and most efficient schema migration method available. Section 4.2 describes how to use PowerDesigner for this purpose. Section 4.3 describes a possible approach to reverse-engineer the schema without PowerDesigner.
4.2 Using Sybase PowerDesigner for database schema migration Sybase PowerDesigner is arguably the most advanced data modeling tool in the market. It is a stand-alone tool, running on Windows. PowerDesigner supports over 30 database types, including Oracle and Sybase ASE. For more information on PowerDesigner, see http://www.sybase.com/powerdesigner . With PowerDesigner it is relatively straightforward to reverse-engineer most of the Oracle schema and convert it to Sybase ASE. The central concept used by PowerDesigner is the PowerDesigner Physical Data Model (PDM). This is a database-independent model which can be converted to the SQL DDL dialect of each supported database.
4.2.1 PowerDesigner schema conversion steps For detailed, step-by-step instructions on how to use PowerDesigner to convert the database schema from Oracle to Sybase ASE, see the document “Migrating an Oracle Database to SAP Sybase ASE with PowerDesigner and ECDA (A Step-By- Step Practical Guide)” at http://www.sybase.com/support/techdocs/migration. Once the schema is reverse-engineered, run the completed DDL script in Sybase ASE and check for any errors.
Note that some aspects of schema migration cannot be handled by PowerDesigner and will have to be handled differently. These aspects are described in section 4.4.
4.3 Reverse-engineering the Oracle schema without Sybase PowerDesigner Without using Sybase PowerDesigner, reverse-engineering the schema can be done in a number of ways: Use the Oracle SQL*Plus DESC command on all database objects, and process the output so that they are valid DDL statements. This is likely to require significant manual script coding. Use the Oracle DBMS_METADATA package to extract DDL for the Oracle objects. This involves SQL statements such as the following (for Oracle table 'MY_TABLE', in schema/user 'SALESAPP'). Note that these are only examples, this is not a complete list of all statement required to perform full reverse-engineering: SELECT DBMS_METADATA.GET_DDL('TABLE', 'MY_TABLE', 'SALESAPP') FROM DUAL; SELECT DBMS_METADATA.GET_DEPENDENT_DDL('INDEX', 'MY_TABLE', 'SALESAPP') FROM DUAL; SELECT DBMS_METADATA.GET_GRANTED_DDL('OBJECT_GRANT', 'SALESAPP') FROM DUAL; Use Oracle SQL Developer (a free Java-based tool, downloadable from oracle.com). This uses the DBMS_METADATA package (see previous bullet). Use TOAD (a low-cost tool, commonly used in many Oracle environments) to extract the object definitions, and then manually convert the Oracle datatypes into their ASE equivalent. This could be cumbersome when large numbers of tables are involved. Once the Oracle schema has been reverse-engineered, the Oracle DDL needs to be converted to Sybase ASE syntax, including conversion from the Oracle datatypes to Sybase ASE datatypes. Section 4.7 describes the mapping from Oracle datatypes to Sybase ASE. In addition, some aspects of the Oracle schema require special attention; see section 4.4.
4.4 Special cases in schema migration The following schema aspects require special attention:
Database Schema Migration 18
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3
Oracle allows more columns per table than Sybase ASE (the limit depends on the ASE server's page size and on the table's lock scheme). If the limit in Sybase ASE is exceeded, an error will be raised when trying to create the table. If this occurs, either the ASE server's page size will need to be increased, or the table needs to be split vertically into multiple tables and all queries referencing the table likely have to be modified accordingly If the length of a column exceeds the maximum allowed length in Sybase ASE (the limit depends on the ASE server's pagesize and on the table's lock scheme), such columns will have to be split into multiple columns and placed in additional tables. All queries referencing the column likely have to be modified accordingly. PowerDesigner converts the Oracle BFILE datatype to the Sybase ASE image datatype. Since BFILE is a datatype used to store a locator (link) to an external binary file stored outside of the database, this is not functionally equivalent so application changes may be required. If a different ASE datatype is required, for example, to hold the name of an externally stored file, change it manually. PowerDesigner 15.x cannot automatically convert the Oracle timestamp datatype to bigdatetime in ASE, so this needs to be done manually. PowerDesigner 16.0 (release expected in August 2011) does not have this limitation and will perform the conversion automatically. PowerDesigner 15.x cannot reverse-engineer Oracle users or security details (permissions). PowerDesigner 16.0 (release expected in August 2011) does not have this limitation and is capable of handling these aspects. Since the SQL reserved words are different between Oracle and Sybase ASE, before attempting a database schema migration, all Oracle objects need to be checked against the Sybase ASE reserved words. Any Oracle identifiers that are also Sybase ASE reserved words, need to be changed first. For a complete list of reserved words in Sybase ASE, see “Adaptive Server Enterprise->Reference Manual: Building Blocks->Reserved Words”. Also see section 4.8 for queries that can be used to search for the occurrence of keywords in the Oracle database. The mapping of Oracle user-defined datatypes to ASE can be difficult and may require extensive manual intervention. The key to user-defined datatype migration is to fully understand the underlying base datatype. Note that user-defined datatypes can be nested. For Oracle, user-defined datatypes is an add-on option to the database and is not widely used.
4.5 Mapping the Oracle schema to Sybase ASE databases Sybase ASE does not have an identical interpretation of the concept of "schema" as the "Oracle schema". When migrating an Oracle schema to Sybase ASE, there are two basic options to map the Oracle schema to Sybase ASE. For the sake of example, let's assume there are two Oracle users john and bill who own an Oracle schema, and each schema has a table named salesdetails. The options are: Perhaps the most straightforward way to migrate, is to map each Oracle schema to a separate ASE database, where each database is owned ('dbo') by the corresponding user. This would result in two ASE databases named john_db and bill_db (different names may of course be chosen), owned by ASE logins john and bill respectively; each database has table named salesdetails, owned by the dbo database user (the full table name would be dbo.salesdetails). However, this results in as many ASE databases as there are users owning an Oracle schema, of which there might be many. While an ASE server can hold up to 32786 databases, it is highly impractical from a DBA perspective to have more than 20-50 databases. Map all Oracle schemas to a single ASE database with a multi-tenancy model. This means that the ASE database user (which is linked to the ASE server login, which is the equivalent of an Oracle user) is used within the database to identify each object's owner. This will result in a more manageable ASE system since there will be less ASE databases. In this case, the example would result in a single ASE database, let's say sales_db, in which ASE logins john
Database Schema Migration 19
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3
and bill have been added as database users. Under each user, a salesdetails table is created, which will have the full name john.salesdetails and bill.salesdetails. Either option is possible; technically ASE does not favor one over the other, but the multi-tenancy model fits best with ASE's methods for backup and restore. It should be noted that multi-tenancy models are sometimes incorrectly seen as security weaknesses since it would be easier for user bill to access john's tables, since they are located in the same ASE database. This is however not justified: if standard best practices around ASE security are followed, then security can be fully guaranteed. One consideration around multi-tenancy databases is that a backup of a database contains the data from all users in that database. If this is undesirable, for example because each user wants to have a backup copy of his own database, then the first option above (separate ASE databases for each user) should be followed instead. Lastly, it may also be the case that there is only one Oracle schema. In that case, there is no need to qualify the ASE tables with the owner name since they will all be owned by the dbo user.
4.6 Schema-related Oracle-Sybase terminology Following is the high-level terminology mapping of Oracle concepts to Sybase concepts. This table is not intended to be used for direct migration purposes, but only as high-level terminology guidance.
Oracle Sybase ASE Database Database Server Schema Database and objects owned by the same user. Tablespace Aspects of ASE database and/or database device and/or segment (system/sysaux tablespaceASE master database; temporary tablespaceASE tempdb database; user-defined tablespacedatabase device and/or segment) Segment A database object that has space allocated (table, index, materialized view) Undo/rollback tablespace Transaction log Online redo logs Transaction log User User, Login (see section 5.5) Role Role Table Table Temporary table Temporary table
View View Materialized View No direct equivalent Cluster No direct equivalent Index Non-unique index
Index-organized table Table with clustered index Column-level check constraint Column-level check constraint
Database Schema Migration 20
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3
Oracle Sybase ASE Column default Column default Unique key Unique key or identity property for a column Primary key Primary key Foreign key Foreign key
Constraints Constraints Collections In PL/SQL, a collection is an ordered group of elements of the same type, such as VARRAYs or nested tables. PL/SQL Procedure Transact-SQL stored procedure PL/SQL Function T-SQL user-defined SQL function (SQL UDF) Triggers Triggers Package No direct equivalent Sequences Partly covered by the identity property for a column or dedicated key value table Snapshot No direct equivalent
Database links, External tables Proxy Tables and Remote Servers
Procedure Stored procedure
Synonym Similar functionality with views for table and view synonyms. All other synonym references must be replaced with fully qualified object strings (database.owner.object) or proxy tables (for synonyms to remote objects).
4.7 Mapping Oracle Datatypes to Sybase ASE The table below describes how Oracle datatypes can be mapped to Sybase ASE datatypes. In most cases the mapping of datatypes is straightforward. For the Oracle datatypes CHAR, VARCHAR2 and RAW, the ASE server page size determines whether or not the mapping can take place; the technical background is that ASE requires a row, and therefore every column, to fit on an ASE database page. By default, ASE uses a 2KB server page size, but 4KB, 8KB and 16KB are also possible. The maximum allowed column length for a column for each ASE server page size depends on various factors such as whether the column is fixed- or variable length and the ASE table's lock scheme. To display full details, run the command dbcc serverlimits in ASE. Oracle Description Sybase ASE Comments / When to use NUMBER(x) Oracle NUMBER(x) datatypes BIGINT length of NUMBER datatype > 10 with 0 decimals can be converted into an equivalent Sybase ASE datatypes. INTEGER length of NUMBER datatype between 6 and 10 and data values <= 2 billion SMALLINT length of NUMBER datatype is between 4 and 5 and data values <=
Database Schema Migration 21
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3
Oracle Description Sybase ASE Comments / When to use 32767 TINYINT length of NUMBER datatype between 2 and 3 and data values <= 255 BIT length of NUMBER datatype = 1 NUMBER(x,y) alternatively to the mapping path NUMERIC(x,y) translates the Oracle NUMBER above, these Sybase ASE DECIMAL(x,y) datatype one-to-one. datatypes can be used. MONEY MONEY and SMALLMONEY store SMALLMONEY monetary data.; 4 digits of precision to the right of the decimal point, and 16 / 6 digits to the left for MONEY / SMALLMONEY respectively. FLOAT maximum FLOAT precision in DOUBLE precision of actual values > 15 Oracle is approx. 38 FLOAT precision of actual values <= 15 CHAR(x) maximum CHAR size in Oracle CHAR(x) if ASE page size is 4kb or greater; and if is 2000 bytes ASE page size is 2kb and x <= 1958 TEXT if none of the above conditions apply VARCHAR2(x) maximum VARCHAR2 size in VARCHAR(x) if ASE page size is 8kb or greater; if Oracle is 4000 bytes for columns ASE page size is 4kb and x <= 3988; if (for PL/SQL variables, the max. ASE page size is 2kb and x <= 1948 size is 32767) TEXT if none of the above conditions apply DATE date/ time precision in Oracle is DATETIME Sybase ASE‟s DATETIME has a up to one second. precision of 1/300th of a second. TIMESTAMP precision of Oracle‟s BIGDATETIME Sybase ASE‟s BIGDATETIME has a [WITH [LOCAL] TIMESTAMP is 1/100000000th precision of 1 microsecond. ASE does TIME ZONE] of a second not support time zones.
ROWID a pseudo column in Oracle, does NUMERIC Also see ROWID on page 62 not represent a true datatype IDENTITY CLOB Oracle‟s max. storage capacity for TEXT Sybase ASE can hold a max. of 2GB CLOB is 128TB per column; IQ can hold up to 2PB NCLOB Oracle‟s max. storage capacity for UNITEXT Sybase ASE can hold a max. of 2GB NCLOB is 128TB per column; IQ can hold up to 2PB BLOB Oracle‟s max. storage capacity for IMAGE Sybase ASE can hold a max. of 2GB BLOB is 128TB per column; IQ can hold up to 2PB LONG Oracle‟s max. storage capacity for TEXT LONG is 2GB RAW(x) the RAW datatype in Oracle has a BINARY(x) if ASE page size is 4kb or greater; and if max precision of 2000 bytes VARBINARY(x) ASE page size is 2kb and x <= 1954 IMAGE if none of the above conditions apply
Database Schema Migration 22
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3
Oracle Description Sybase ASE Comments / When to use LONG RAW Oracle‟s max. storage capacity for IMAGE LONG RAW is 2GB CHAR(1) if this is a packed bit column BIT maintained by a PL/SQL function set / unset / retrieve / query on them. BFILE BFILE stores a locator (link) to a no direct equivalent binary file outside of the database
4.7.1 Chained Oracle data rows Oracle allows long data rows to exceed the size of a disk block. This is known as 'chained rows'. It is possible that such chained data rows, if they exist in the Oracle database, are too long to be stored in Sybase ASE, which requires that a data rows fits on a data page (which is 2KB, 4KB, 8KB or 16KB; use dbcc serverlimits to find the net max row length allowed in ASE). Also, for tables with more than 255 columns, the rows will always be chained. It is important to identify tables that have chained rows before starting the migration. To find how many chained rows occur in a table, run this Oracle query: SELECT owner, table_name, chain_cnt FROM dba_tables WHERE chain_cnt > 0
If chained rows are found, the Oracle command ANALYZE TABLE table-name LIST CHAINED ROWS INTO chained-row-table can be used to identify the actual chained rows. If chained rows are found, it may be needed to modify the data model to ensure that rows are short enough to fit on an ASE page.
4.8 Search for Sybase ASE reserved words and keywords in Oracle Before you can migrate an Oracle schema or Oracle stored procedure, function or trigger, there needs to be a check for reserved words (keywords) that are already identified as either problematic or non-migratable. Oracle allows SQL keywords to be used as identifiers whereas this is not allowed in ASE. For example, the following is valid PL/SQL: CREATE TABLE case (begin VARCHAR2(100), when INT) The following query finds all object names within the Oracle database that are ASE keywords: select owner, object_name, object_type FROM sys.dba_objects WHERE object_name = UPPER('
Database Schema Migration 23
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3
SELECT name FROM master..spt_values WHERE type = 'W'
4.9 Choosing a lock scheme for Sybase ASE tables ASE offers a choice of three lock schemes for each database table: allpages, datapages or datarows. allpages is the oldest lock scheme, as well as the out-of-the-box ASE default. It is slightly more efficient for some types of operations. The datapages, and especially datarows, lock schemes provide fundamentally better concurrency characteristics. The concurrency benefits are likely to be relevant when migrating from Oracle to Sybase ASE due to the difference in transaction handling (as described in chapter 8). It is recommended to configure datapages or datarows as the default lock scheme in Sybase ASE. datapages is more efficient, but datarows provides better concurrency (datarows locking is also known as row-level locking). Changing between datarows and datapages for an existing table is instantaneous. In contrast, large tables with the allpages lock scheme may require long downtimes to if their lock schemes need to be changed to datarows or datapages since this requires a full conversion of the table and all its indexes.
4.10 The Oracle DUAL Table In Oracle, a SELECT statement must always be executed against a table, even when retrieving system information, such as the current date/time. For this purpose, Oracle created the DUAL table. Retrieving the system date via SQL looks like this in Oracle: SELECT sysdate FROM DUAL
Sybase ASE supports SELECT statements that do not have a FROM clause. The same query in Sybase ASE would look like this: SELECT getdate()
To avoid rewriting existing SELECTs that use the DUAL table, it is possible to create a table named DUAL in ASE, which must always contain one and only row:
create table DUAL (dummy_col char(1) unique check (dummy_col='X')) insert DUAL values ('X') go
If Sybase ASE is created case-sensitive (see section 5.2), you may need to create additional tables named dual, Dual, etc, depending on how disciplined the Oracle developers were in using a consistent spelling for the DUAL table. Alternatively, consider editing the Oracle PL/SQL source code to use only "DUAL", or to remove all references to DUAL completely.
Database Schema Migration 24
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3
5 MIGRATING SERVER-LEVEL ASPECTS The architecture of the database server, and the way it is configured and managed, are quite different between Oracle and Sybase ASE. This chapter lists some migration aspects that require attention, but without claim for completeness. The reader is urged to consult the Sybase documentation, specifically the "System Administration Guide", for full details.
5.1 Character set When creating a new Sybase ASE server, the character set to be used by the ASE server must be chosen. It is recommended to use the same character for ASE, as is being used for the Oracle database. While the character set in ASE can be changed at a later point in time, it is strongly recommended to avoid this, and to pick the right character set before migrating any Oracle aspects to ASE.
5.2 Database server case sensitivity ('sort order') A difference between Oracle and Sybase ASE is that Oracle is not case-sensitive, whereas Sybase ASE is case-sensitive by default. ASE can be configured to be case-insensitive, by installing a case-insensitive 'sort order'. Moreover, there is also a difference in the scope of case-insensitivity between Oracle and ASE: In a case-insensitive ASE server, case-insensitivity applies to both identifiers and to data comparisons; SQL keywords are always case-insensitive in ASE. In Oracle, case-insensitivity applies only to identifiers (table names, column names, etc), but, by default, not to data comparisons; it is likely that existing Oracle systems use this default. Note that the above applies only to unquoted identifiers; quoted identifiers are case-sensitive in Oracle, though these are not used often. As a result, the following two queries will retrieve different data in a case-insensitive Oracle system, but retrieve the same data in a case-insensitive Sybase ASE: select * from Employees where Name = 'Johnson' select * from Employees where Name = 'JOHNSON'
Also, existing Oracle SQL code refers to the table TEST in different ways - the following all refer to the same table. Inconsistent use of upper- and lower-case spelling for identifiers is not uncommon to occur in practical Oracle systems: select * from TEST select * from Test select * from test When using a case-insensitive sort order for Sybase ASE, such SQL statements do not need to be changed. When using the default case-sensitive ASE sort order, all references to a table must use the exact same upper/lowercase spelling, or "table not found" errors will result.
Whether the ASE server should be case-sensitive or case-insensitive is a decision to be made. For ASE, there is no overriding technical advantage to either option. In practice, the decision probably depends on whether query results may be affected by using a case-insensitive ASE server. If this is the case, then the default case-sensitive ASE configuration should be used, and any Oracle SQL statements referring to identifiers in mixed-case spelling (i.e. TEST and Test) should be changed to use one consistent spelling for the identifiers.
Migrating server-level aspects 25
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3
5.3 Server configuration parameters In Oracle, the configuration parameters for the server and database are stored in the initialization file (init.ora) or server parameter file (spfile). These parameters cover a diverse set of resources, such as memory, processes, network, disk, I/O, connections, files, character set, and so on. It is unlikely that Oracle configuration parameters can be mapped directly to corresponding configuration parameters for Sybase ASE. It may however be useful to be aware of Oracle-specific configuration settings since in some cases some kind of Sybase ASE equivalent could be required. The non-default values of the Oracle parameters can be obtained using one of the following options: Convert the server parameter file (spfile) to an initialization parameter file as follows: CREATE pfile FROM spfile Query the database by executing the following statement: SELECT name, value FROM sys.v$spparameter WHERE isspecified = 'TRUE'
5.4 Storage Most Oracle installations enlist the help of Oracle‟s Automated Storage Manager (ASM). Sybase ASE does not have the equivalent of ASM. Storage must be managed through T-SQL commands, Sybase Control Center , or via Sybase Central (the Sybase database admin GUI tool). Generally speaking, Sybase ASE recommends the following high-level guidelines for storage: For user databases, use raw devices or filesystem devices with directio=true. Never use filesystem devices with dsync=false for user databases; filesystem devices with dsync=true can be used but carry a potentially significant performance penalty For temporary databases, filesystem devices with dsync=false are generally recommended. For the underlying storage layer, RAID 0+1 or RAID 1+0 is recommended. Avoid RAID 5 for write-intensive purposes such as the ASE transaction log, unless the storage solution provides a non-volatile write cache to buffer the writes. To achieve maximum disk I/O bandwidth, read- and write-intensive data should preferably be spread over as many physical spindles as possible. Many additional considerations with respect to storage configuration apply. Please refer to the Sybase ASE "System Administration Guide" for details.
5.5 Migrating the User Logins There are some differences in terminology between Oracle and Sybase ASE around the concept of a "user". In Oracle, on instance level: a user is used for authentication, and can also be a schema owner (and thus own database objects, and have permissions on database objects)
In Sybase ASE, on server level: a login is used for authentication, but does not own any objects or have object access permission. A special ASE login is sa - this is the 'super user' in Sybase ASE, comparable to the SYS account in Oracle. This user has access permissions on all database objects and should be restricted to the DBA. For security reasons, applications should never use the sa login to connect to the ASE server.
Migrating server-level aspects 26
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3
In Sybase ASE, on database level: a user, which maps to a login, can own database objects and have permissions on database objects. When migrating from Oracle to Sybase ASE, the most likely scenario is to migrate all Oracle application users to an identically named Sybase ASE login. For each ASE login, a corresponding database user (typically with the same name as the login) is then created to allow that login to access an ASE user database. A login can be given access to multiple ASE databases by creating a corresponding database user in each ASE database. Alternatively, the guest database user can be created in each ASE user database. However, related security implications should be carefully assessed first. The resulting structure of ASE logins and database users depends on decisions about how an Oracle schema is migrated to ASE (see section 4.5).
5.5.1 User passwords Each Oracle user has a password. In ASE, a login has a password. If the Oracle user passwords are known, they can be set identically in ASE; otherwise, new passwords must be set for the ASE logins. ASE login passwords cannot be set to blanks.
5.6 Permissions It is recommended to use PowerDesigner 16 to reverse-engineer the permissions for accessing (objects in) the Oracle database. If PowerDesigner 16 cannot be used, the permissions will likely have to be converted manually to the Sybase ASE equivalent.
Migrating server-level aspects 27
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3
6 DATA MIGRATION This section describes the methods for migrating data from Oracle to Sybase ASE. It is assumed that the schema has already been migrated. The main complicating factor is that Oracle provides no tools to unload a table to a flat file in a format that can be read by non-Oracle tools. Data migration can be performed in a number of ways. Therefore, when choosing an approach, various factors need to be considered, including: - the complexity of the chosen solution - the volume of data being migrated - the available system downtime to perform the data migration during cutover - the need to become familiar with new software or tools for the purpose of migrating the data - additional software license costs
In essence, the following options are available for data migration: Unload Oracle data into ASCII-formatted flat files, and load these files into ASE with the Sybase "bcp" utility. If Oracle data can be exported into an ASCII-formatted flat file, then ASE's high-speed loading tool "bcp" can load it into ASE. Since Oracle does not provide a way to achieve this, the user must either use a 3rd-party tool for this purpose, or create his own PL/SQL utility to essentially spool the data from the database into a flat file. Considerations: This option is often seen as attractive due to the transparency of the migration process: all steps are clearly visible and can be individually developed and tested. Developing your own PL/SQL tool to unload Oracle data is simple, but will perform slowly, thus making it unsuitable for anything but relatively small data volumes. Using a 3rd-party tool adds software license costs. Use Sybase's Enterprise Connect Data Access (ECDA) Option for Oracle. ECDA is a connectivity product by Sybase that enables direct connections from an ASE database into an Oracle database, making it possible to transfer Oracle data directly into ASE. ECDA hooks into the ASE mechanism of "proxy tables". Considerations: This option can be used when the data volume is such that the data can be transferred in the available migration window. It is unlikely to be suitable for very large data volumes. An advantage is that ECDA takes care of mapping Oracle datatypes to ASE datatypes, and that the migration can be fully performed through SQL. Using this option requires purchasing Sybase's ECDA product. Use Sybase Replication Server Heterogeneous Edition (RSHE) for Oracle Sybase Replication Server captures database transactions in Oracle and applies these to ASE, thus keeping the ASE database continuously up-to-date. In addition, Replication Server can also initially copy the full contents of the Oracle tables into ASE, in order to initialize the data replication ("materialization of the replication system"). Considerations: Using transactional replication is the only data migration solution where activity on the Oracle database can continue while the data migration is in progress. This means that the migration downtime, during which applications are not available because they must switch from the Oracle database to the ASE database, is independent of the data volume being migrated; this downtime could potentially be very short (e.g. minutes rather than hours). Using this option requires purchasing Sybase's Replication Server product, as well as learning how to use Replication Server. Letting Replication Server perform the initial data copy from Oracle to ASE may not be realistic for large data volumes. In this case, the initial materialization of the replication system might be better performed with one of the other options mentioned here. Use a 3rd-party ETL tool that supports both Oracle and Sybase ASE.
Data Migration 28
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3
Considerations: This option is most attractive if the ETL tool is already in use so that no additional software needs to be purchased for the migration alone. an be used when the data volume is such that the data can be transferred in the available migration window. It can be used for very large data volumes, but a sizeable migration window may be required.
6.1 Unload Oracle data into ASCII files; load into ASE with "bcp" utility ASE's high-speed data loading utility "bcp" is capable of loading almost any type of appropriately formatted ASCII data file into ASE. However, since Oracle does not provide any tools to export Oracle data into an ASCII-formatted file, the user must either use a 3rd-party tool for this purpose, or create his own PL/SQL utility to essentially spool the data from the database into a flat file. FACT is an example of such a 3-rd party tool.
6.1.1 Loading into ASE with "bcp" This is an example of loading data from an ASCII file into an ASE table (named mydb..mytable) with bcp: bcp mydb..mytable in mytable.txt –Ulogin –Ppassword –Sserver –c In practical situations, bcp should also specify which row- and column delimiters are used (bcp -r and -t options) since the defaults (CR and tab) could also occur in the actual data file (which is ASCII, after all). When unloading data into flat ASCII files, proper delimiters should be chosen. Bcp-in performance is best when all indexes on the tables being loaded, are dropped first. Of course, , depending on the size and number of indexes and the width of the base tables, recreating them afterwards could take a long time on large tables, so this may not be realistic for all cases. It is usually best to use a large network packet size with bcp (the –A option; also requires configuring the network packet size on the ASE server). For large tables, it may be advisable to use the bcp –b option to break the load into multiple database transactions. This is typically combined with enabling the "trunc log on checkpt" database option in ASE to avoid the transaction log filling up. To load only part of a data file, or to load columns in a different order than in the file, a so-called "bcp format file" may be used. For more information on format files, as well as on bcp in general, see the Utility Guide in the ASE documentation set (http://tinyurl.com/6883kx4). It is highly recommended to perform multiple bcp operations in parallel (one for each table being loaded). The optimal number of concurrent bcp operations will be determined by the hardware capabilities. If there is only one (or few) large tables that need to be loaded, these can still be loaded using in multiple BCP operations by adding partitioning the table using round robin partitioning and specifying the start and last rows of the data file being loaded into a particular partition number of the table. Lastly, note that, on Unix/Linux, bcp can read from a "named pipe" (created with the "mkfifo" command). If the utility that extracts the data into a file can write to a named pipe as well, then a lot of time can potentially be saved as follows: 1. Create a named pipe with the Unix/Linux "mkfifo" command 2. Extract the data from Oracle, writing it to the named pipe. 3. Without waiting for the data extraction to complete, start bcp to load the data from the same named pipe. Bcp will read data from the named pipe once it is delivered by the extraction utility, and immediately insert it into ASE. Instead of first extracting the data and then loading it, the time to transfer the data is now reduced to the longer of (extracting the data, loading the data). This can represent significant time gain. For more information on bcp and named pipes, please refer to http://tinyurl.com/5urcfrt .
6.1.2 Unloading from Oracle: FACT (3rd-party tool) FACT ("Fast Extract") is a 3rd-party high speed Oracle data export tool that allows ASCII flat file creation, also in parallel mode. These files can be used as input for the Sybase ASE utility bcp.
Data Migration 29
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3
For more information about FACT, see http://www.iri.com/products/FACT.
6.1.3 Unloading from Oracle: Roll-your-own PL/SQL utility to export Oracle data If you want to unload data from Oracle tables into ASCII flat files using only Oracle features, you must create your own PL/SQL utility that essentially spools the data from the database into a flat file. This uses the DBMS_OUTPUT.put_line command in PL/SQL. Here's an example of exporting two columns of table emp using "~" as a column delimiter and CR as a row delimiter. The output from this PL/SQL code should be captured in a flat file:
DECLARE CURSOR emp_cur IS SELECT ename, sal FROM emp; BEGIN FOR emp_rec IN emp_cur LOOP DBMS_OUTPUT.PUT_LINE (emp_rec.ename || '~' || TO_CHAR (emp_rec.sal) ); END LOOP; END; /
The downside is that this method is likely to be very slow, making it unsuitable for anything but relatively small data volumes. In addition, care must be taken to correctly format/convert each column datatype management.
6.1.4 Unloading from Oracle: use Oracle SQL Developer Oracle SQL Developer is a free Java-based tool, downloadable from oracle.com. This can be used to create a logical export of the data, whereby a SQL INSERT statement is created for every row. The downside is that this method is likely to be relatively slow in exporting as well as importing the extracted data, since this is all done on a single-row basis. This may make it unsuitable for large data volumes.
6.2 Use Sybase's Enterprise Connect Data Access (ECDA) Option for Oracle ECDA is a connectivity product by Sybase that acts as a gateway between Oracle and Sybase ASE. With ECDA, direct connections can be made from an ASE database into an Oracle database, making it possible to transfer Oracle data directly into ASE using only SQL. The ECDA functionality is exposed as an ASE "proxy table", which maps to the actual Oracle table. By selecting from the proxy table, data is retrieved from the Oracle table and can be inserted directly into an ASE table. Also, it is possible to do things like joining Oracle tables (though their proxy table) with tables in Sybase ASE. The main advantage of using ECDA is that takes care automatically of the datatype conversions from Oracle to Sybase ASE when the data is retrieved. It also offers the flexibility and control of using the SQL language to access to proxy tables. ECDA involves starting a separate process outside the ASE server.
6.2.1 ECDA Example For examples of how to use ECDA in an Oracle migration context, see the document “Migrating an Oracle Database to SAP Sybase ASE with PowerDesigner and ECDA (A Step-By-Step Practical Guide)” at http://www.sybase.com/support/techdocs/migration.
6.3 Use Sybase Replication Server Heterogeneous Edition (RSHE) for Oracle Sybase Replication Server is often used by Sybase customers to facilitate migrations between databases. The main attraction is that the required downtime for curring over from the "old" to the "new" database can in principle be very short as far as the database side of things is concerned.
6.3.1 Minimal migration downtime with Replication Replication Server captures database transactions in Oracle by reading the Oracle redo logs, and then applies these transactions to ASE, thus keeping the ASE database continuously up-to-date. In addition, Replication Server can also
Data Migration 30
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3 initially copy the full contents of the Oracle tables into ASE, in order to initialize the data replication ("materialization of the replication system"). When large tables are involved, a main decision to be made is whether this initial materialization needs to be performed through Replication Server or through an external unload-and-load mechanism. When using Replication Server for data migration, the objective is to reach a state where the ASE database is completely in synch with the Oracle database, at which point the applications can switch from the Oracle database to the ASE database (after the cutover, the replication setup can be removed). The system downtime needs to be only as long as this application cutover takes, which would typically rather be minutes rather than hours. It is essential to observe that replication is application-transparent: applications can keep working normally on the Oracle database until the moment of cutover comes (obviously, the applications themselves likely require modifications to run on an ASE database instead of Oracle, but that is outside the scope of this topic of data migration). Other data migration solutions than transactional replication will require significantly more downtime. This is because Replication Server provides a mechanism to incrementally upload data changes from Oracle to ASE allowing applications continue to work normally. In contrast, most other migration methods essentially take a copy of an entire table which usually requires applications to be shut down or in read-only mode since it can be very difficult to reconcile any data changes to the copied afterwards. For those other migration methods, the required system downtime is therefore roughly identical to the time required to copy the data out of Oracle and into Sybase.
6.3.2 Initial materialization for the replication setup Replication Server can automatically copy the full contents of the Oracle tables into ASE, in order to initialize the data replication ("materialization of the replication system"). However, for very large tables, this may take unacceptably long. An alternative approach may therefore be to take an initial copy from these large tables through other means, like one of the other options described in this section on data migration (for example, unload into an ASCII flat file and load into ASE with bcp). With Replication Server, changes made to the table afterwards will be synch'd afterwards. The high-level approach would be as follows: 1. Set up table replication for all Oracle tables to ASE tables, but do not auto-materialize the large tables. Optionally, enable "autocorrection" for the large tables (depending on your understanding of the type of data changes that may be made; see the Replication Server documentation for details). 2. Suspend the DSI connection by Replication Server to the ASE database. Any future changes to the Oracle tables will be picked up by Replication Server and are accumulated in Replication Server's "stable queues". At a later point, these changes will be applied to ASE. 3. For the large tables, take a copy and load this into ASE (using your preferred method). 4. Once the loading of the large tables into ASE is complete, resume the connection from Replication Server to the ASE database. This will push out the changes that were accumulated in Replication Server's "stable queues", and apply these to the ASE tables. 5. Once all accumulated changes are pushed out to ASE, the ASE database should be in the same state as the Oracle database and the applications can switch over to complete the migration. When the tables are not too large to perform automatic materialization, or when it is acceptable that such materialization takes a long time (since the Oracle applications keep functioning normally anyway), then the above steps can be replaced by simple setting up table replication from Oracle to ASE using automatic materialization.
6.3.3 Other considerations Using this option requires purchasing Sybase's Replication Server Heterogeneous Edition (RSHE) for Oracle, as well as learning how to use Replication Server. Letting Replication Server perform the initial data copy from Oracle to ASE may not be realistic for large data volumes. In this case, the initial materialization of the replication system might be better performed with one of the other options mentioned here. Before using Sybase Replication Server to replicate out of an Oracle database, verify whether this complies with the available Oracle licenses. If a full Oracle license is used, there should be no restrictions; if a more restricted Oracle
Data Migration 31
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3 license is used (like a run-time only license), this might legally prohibit use of Replication Server and additional Oracle licensing might be needed. This is a matter outside the scope of Sybase, and should be addressed with Oracle. Oracle GoldenGate can also provide transactional replication between Oracle and Sybase ASE. If the customer already has this product available, in principle this can also be used as part of a migration, in similar ways as described above for Sybase Replication Server.
6.4 Use a 3rd-party ETL tool that supports both Oracle and Sybase ASE If an ETL tool is already in use which supports both Oracle and Sybase, it may be attractive to use it to perform the data migration. Typically this would require system downtime for the duration of transferring the data from Oracle to Sybase, unless the ETL tool is capable of sorting out any changes to the data that are made during the transfer process.
Please make sure that you adhere to any license restrictions and clear the use of this tool to move data from Oracle to Sybase ASE with this vendor.
6.5 Oracle datatypes requiring special attention for migration The following Oracle datatypes require special attention when migrating the data.
Oracle TIMESTAMP Sybase BIGDATETIME Oracle‟s TIMESTAMP datatype has a granularity of 1/100000000th of a second. This exceeds the precision of Sybase‟s BIGDATETIME datatype which has a granularity of 1 microsecond. When migrating data with bcp, TIMESTAMP data may need to be edited to remove the last 3 digits to avoid bcp throwing an error.
Oracle BLOB/CLOB/NCLOB Sybase IMAGE/TEXT /UNITEXT Oracle stores large binary objects in the BLOB datatype and large character objects in the CLOB datatype. Both datatypes can store up to 128TB (4GB * database block size) of data, as of Oracle 11g. When migrating, data from Oracle‟s BLOB datatype should be mapped to Sybase IMAGE datatype and CLOB to the TEXT datatype. The maximum size for an individual column value of the IMAGE or TEXT datatype in Sybase ASE is 2GB. If the actual Oracle data values are larger than this maximum, ASE is unable to store these values. In this case, Sybase IQ might be a solution since it supports a maximum varying between 512TB to 2PB per column value.
Oracle BFILE The Oracle BFILE datatype is used to store a locator (link) to an external binary file stored outside of the database. Sybase ASE has no direct functional equivalent, so application changes may be required.
Data Migration 32
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3
7 MIGRATING PL/SQL TO TRANSACT-SQL PL/SQL is Oracle's implementation of the SQL language. Transact-SQL (T-SQL) is Sybase ASE's SQL dialect. Both SQL versions are mostly ANSI-92 entry-level compliant, but both vendors have implemented extensive non- ANSI-compliant vendor-specific enhancements and extensions. In many cases both dialects will still have equivalent functionality in their vendor-specific extensions, but syntax changes or varying amounts of code changes may be required when migrating from PL/SQL to T-SQL. In cases where T-SQL does not have a direct equivalent of a particular PL/SQL construct, larger amounts of code rewrite or even application rewrite could be required. While the incompatibilities between Oracle and Sybase are quite limited when it comes to schema migration and data migration, there is much more potential for migration complexity between the two SQL dialect. Consequently, migrating PL/SQL to T-SQL is probably the most involved part of any Oracle to Sybase migration, and will typically require manual conversion/migration activity. A key factor for a successful migration –or, for that matter, for avoiding a failed migration- is a realistic assessment of the SQL-related complexities to be migrated before starting the migration project. Chapter 3 provides checklists for this purpose. To assist with the actual migration of PL/SQL to T-SQL, chapter 11 contains a cross-reference between Oracle features and their Sybase ASE equivalents, in three categories of complexity. This cross-reference is an extended version of the Oracle checklist in chapter 3 but provides more detail and provides specific suggestions on how to migrate a specific Oracle feature to ASE.
7.1 Locations of PL/SQL code PL/SQL code can be found in the following locations: Stored procedures (in the database server) Triggers (in the database server) SQL functions (in the database server) SQL queries (submitted to the database server by client applications, for example as anonymous PL/SQL blocks)
PL/SQL objects in the database server can be reverse-engineered, or, if present and up-to-date, repository scripts that were used to create these PL/SQL objects can be taken as a starting point. PL/SQL code located in client applications needs to be identified in a different way, for example source code inspection
When it comes to using existing scripts or reverse-engineering the PL/SQL objects from the database server, the same considerations apply as with respect to the database schema; see the pros and cons discussed in section 4.1. Sybase PowerDesigner may also be used to reverse-engineer PL/SQL objects (see section 4.2); however PowerDesigner does not perform any conversion to T-SQL (for this, evaluate tools as in section 7.2 below).
Since the majority of PL/SQL is typically located in stored procedures and triggers, "migrating PL/SQL" is often equated to "migrating stored procedures and triggers". While that definition is not formally correct (there are other places where PL/SQL occurs, as shown above), it does reflect the area where most migration issues are typically encountered.
7.2 3rd-party tools for PL/SQL migration to T-SQL Tools for migrating from PL/SQL to T-SQL would be a welcome help when undertaking Oracle to ASE migrations. However, it is unlikely that any automated tool will be capable of perfectly migrating all of the PL/SQL code in any real- life Oracle system to ASE's T-SQL. Yet, it may well be possible that a substantial percentage can be handled by a tool, but a certain amount of manual conversion/migration should be expected.
Migrating PL/SQL to Transact-SQL 33
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3
SwisSQL and SQLWays (both 3rd-part tools) are among the few tools that provide assistance with automatic migration of Oracle PL/SQL code to Sybase T-SQL. For more information, see www.swissql.com (SwisSQL) and www.ispirer.com (SQLWays). It should be noted that for both tools, support for ASE features in general, and new features in ASE 15.0 and later in particular, appears to be limited. It is recommended to carefully evaluate these tools before using them for PL/SQL migration. Please note that the above neither constitutes an endorsement by SAP/Sybase of either SwisSQL or SQLWays, nor a statement about the suitability of these tools for any specific project or purpose.
Migrating PL/SQL to Transact-SQL 34
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3
8 TRANSACTIONS AND LOCKING, ORACLE VS. SYBASE The topic of transaction handling, transaction isolation and locking is probably where the most profound differences between Oracle and Sybase ASE occur. For this reason a separate chapter is dedicated to this topic.
8.1 Oracle MVCC vs. Sybase locking The purpose of transactions in the database is to take the database from one consistent state to the next. Database transactions, both in Oracle and Sybase ASE, guarantee all of the ANSI-defined ACID characteristics. ACID is an acronym for: Atomic: Either all of the modifications in the transaction are applied or none is applied. Consistent: A transaction takes the database from one consistent state to the next, observing referential integrity constraints. Isolated: The effects of a user's transaction are not visible to other users until the transaction is committed. Durable: Once the transaction is successfully committed, it is permanent.
Oracle's implementation of the "Isolation" aspect of transactions is different from Sybase ASE's. Oracle uses MVCC (multi-version concurrency control) where an open transaction creates a new version of the data it is modifying, such that other sessions reading the same data will read the unmodified version, and thus are not blocked ("writers don‟t block readers and readers don't block writers"). In contrast, Sybase ASE maintains only a single version of the data, and uses blocking locks to implement transaction isolation. Oracle also uses locking in addition to MVCC, but Oracle's locking concept is rather different from ASE's.
8.2 Transaction-related migration issues The different approaches towards transaction isolation by Oracle and Sybase ASE may bring up the following issues when migrating from Oracle to ASE:
Oracle applications and queries may rely, knowingly or unknowingly, on Oracle MVCC's "writers don't block readers and readers don't block writers" behavior. When migrating such queries unchanged to Sybase ASE, concurrency problems (blocking) may result. In addition, since MVCC has the effect that the result of an Oracle query is essentially defined at the moment then the query starts, different results could potentially be returned.
Long-running transactions: these are fine, and indeed common, in Oracle where MVCC allows transactions to remain open for longer times with fewer adverse effects (though naturally, this also has its limits; for example writers still block writers). With Sybase ASE designed specifically for high-performance OLTP, transactions should be kept as short as possible in ASE for best concurrency and performance. Long transactions in ASE can quickly lead to issues around concurrency (blocking) and resource consumption which also affects unrelated transactions by other users (transaction log full).
Oracle uses implicit transactions (also called "chained transactions"). This means a transaction is started automatically whenever a SELECT, INSERT, UPDATE or DELETE statement is executed. By default Sybase ASE uses explicit transactions ("unchained"), though it also supports the ANSI-compliant implicit/chained mode as well. When migrating to ASE, it may be needed to run some transactions in chained mode which could involve making changes to the way some transactions are handled, notably changing the transaction mode at session or client level, or by adding explicit BEGIN TRANSACTION statements (which Oracle does not support nor require).
Transactions and Locking, Oracle vs. Sybase 35
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3
For a successful migration to Sybase ASE, it is crucial to have a thorough understanding of the behavior of the Oracle application on the above aspects, and of the assumptions behind the design of queries and transaction handling in the Oracle application.
8.3 Using ASE implicit/chained transaction mode The most straightforward migration option with respect to Oracle's implicit/chained transaction mode is to retain the transactional structure of the Oracle application, and operate Sybase ASE in chained transaction mode. In Sybase ASE, implicit/chained transaction mode can be achieved by:
Running the T-SQL command SET CHAINED ON before starting a transaction. This statement can also be executed in an ASE login trigger. Setting the OpenClient connection attribute CS_OPT_CHAINXACTS to true (default=false) in the client application before connecting to the ASE server (With the isql utility, this attribute is set by specifying the -Y command-line flag). Since some operations in Sybase ASE may not work in chained mode, for example administration procedures such as sp_configure, always enabling chained mode for all connections may not be practical (although ASE 15.7 allows various system sp_* procedures to run in chained mode). It is recommended to only enable chained mode for those connections or stored procedures that really require it. For connections by the DBA (typically, the 'sa' user), the default unchained mode should always be used instead.
8.3.1 Transactional DDL When running Sybase ASE in chained mode, it is possible that, with a straightforward migration from Oracle, DDL statements are executed inside a transaction. By default, this will cause an error in Sybase ASE. To allow DDL statements in a transaction in ASE, run: sp_dboption database_name,'ddl in tran', true . Note that this is not possible for some types of DDL.
In addition, Oracle issues an implicit COMMIT after each DDL statement. In ASE, an explicit COMMIT statement should be inserted after each DDL statement that runs in a transaction to avoid concurrency issues. Alternatively, chained mode should temporarily be turned off at session level when DDL is executed.
8.3.2 Transaction processing in stored procedures If transaction processing is performed inside stored procedures, and the transaction mode (chained/unchained) matters, Sybase ASE optionally allows enforcing that a stored procedure is executed only in chained or unchained mode (or either mode). This can be achieved with sp_procxmode: sp_procxmode proc_name, { 'chained' |'unchained' | 'anymode' }
8.4 Using ASE explicit/unchained transaction mode If it appears that running ASE in implicit/chained transaction mode leads to too many concurrency issues, consider using the default ASE explicit/unchained mode instead for all transaction or only for selected transactions. When using unchained transaction mode, a BEGIN TRAN[SACTION] statement needs to be added to all transactions that will run in unchained mode (this statement is not required in chained mode where transactions start implicitly). To determine the best location to add BEGIN TRANSACTION requires detailed understanding of the transaction in question. In general it is recommended to keep transaction in ASE as short as possible.
8.5 Using ASE transactional concurrency enhancements Oracle's MVCC feature tends to be seen, especially by Oracle itself, as a vastly superior and irreplaceable transaction handling model, compared with other database brands.
Transactions and Locking, Oracle vs. Sybase 36
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3
In reality, much of the concurrency benefits of MVCC can be achieved in Sybase ASE by using ASE-specific features. What is true is that concurrency issues caused by sub-optimal transaction/query design will be less immediately visible in Oracle than in ASE; consequently, discipline in transaction programming is more important in Sybase ASE than in Oracle since sloppy transaction handling backfires quicker in Sybase ASE than in Oracle.
When migrating from Oracle, it is recommended to consider the use of the following ASE features: Choose the datapages or datarows lock scheme for database tables. These lock schemes provide better concurrency than the default of allpages which is likely to be relevant when migrating from Oracle to ASE (also see section 4.9). When using datarows locking, uncommitted inserts do not block readers; in addition, "pseudo- column-level locking" behavior will automatically apply in certain scenarios (see the ASE Performance and Tuning manual, volume "Locking and Concurrency Control" for details). Consider using the readpast feature in queries. When reading data, this lets the query skip over locks that would otherwise have blocked the read operation. For example: select * from mytable readpast where mykey = 123 When using readpast, the data page (with datapages lock scheme) or data row (with datarows) being locked and skipped over, will not be read. In many cases however, this may be acceptable because the nature or timing of the query is such that the data being looked for is known not to be accessed by other users anyway. Or the skipped data is known not to have any impact on the query result anyway.
Consider using the ANSI transaction isolation level 0 (ANSI READ UNCOMMITTED) in SELECT queries. While reading, this lets the SELECT query read data that is currently locked, and potentially being updated, by another user's transaction. On the default ANSI transaction isolation level 1 (READ COMMITTED), the SELECT query would be blocked instead. When using ANSI isolation level 0, it is important to be aware of the implications and potential downsides, such as requirements for unique indexing, the risk of isolation level 0 select queries being aborted in certain scenarios (see the see the ASE Performance & Tuning manual, volume "Locking and Concurrency Control" for details). Also, since isolation level 0 does not provide true transaction isolation, there is the risk of reading data that is currently being updated and which may be updated again, or rolled back, after being read. However, this may be acceptable because the uncommitted data being read is known not to have any impact on the query result anyway. When using transaction isolation level 0, it is strongly recommended not to set this as the default isolation level for a session, but to add the clause AT ISOLATION READ UNCOMMITTED or AT ISOLATION 0 only to those SELECT statements where isolation level 0 is required.
8.6 Other transactional aspects
Savepoints: Sybase ASE supports savepoints in the same way as Oracle though with slightly different syntax.
By default, Oracle operates on transaction isolation level 1 (READ COMMITTED), which is the same as Sybase ASE. Oracle also supports transaction level 3 (SERIALIZABLE). Sybase ASE supports both isolation levels as well. (Note that Oracle does not support isolation levels 0 and 2).
SQL*Plus commit behavior: o Oracle's SQL*Plus always commits when exiting normally. Sybase's isql client does not commit when it exits, and consequently the effect would be that any open transaction is rolled back – which is the opposite of Oracle's SQL*Plus behavior. o Oracle's SQL*Plus can be configured to autocommit after every statement with SET AUTOCOMMIT ON; by default, this is disabled. Sybase's isql client does not support autocommit; to achieve the same effect, explicit COMMIT statements should be inserted.
Transactions and Locking, Oracle vs. Sybase 37
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3
Oracle supports the syntax SET TRANSACTION READ ONLY, which makes the data read during the transaction transactional data read-only, thus achieving the almost the same effect as transaction isolation level 3 (SERIALIZABLE). In Sybase ASE, this should be changed to using transaction isolation level 3 (SERIALIZABLE). This can be achieved with either of the following syntax: o SET TRANSACTION ISOLATION LEVEL 3 o SELECT … AT ISOLATION LEVEL 3
Instead of ISOLATION LEVEL 3, ISOLATION LEVEL SERIALIZABLE can also be used. Oracle also supports the syntax SET TRANSACTION READ WRITE; this can be removed when migrating to Sybase ASE since it is the default transactional behavior. Deadlocks: Oracle sometimes pictures other database brands that do not support MVCC, as a source of 'deadlocks', perhaps aiming to use this somewhat scary-sounding terminology as an argument against their competitors. Indeed, deadlocks are rare in an Oracle environment, although it should be noted (consult any computer science textbook on concurrent computing) that the possibility of deadlocks can never be excluded in a multi-user environment – which includes Oracle databases. When following some elementary best practices, deadlocks typically do not occur at all, or very rarely at worst, in Sybase ASE. The main guideline to avoid deadlocks is that when different transactions each access multiple tables, they should always do so in the same order. In addition, using the ASE datarows lock scheme will help to reduce the chance of deadlocks occurring. Finally, in the rare occasion that deadlocks do occur, it is recommended to implement deadlock retry logic into the application where possible. In summary, deadlocks need not be a major point of concern when migrating from Oracle to Sybase ASE.
Transactions and Locking, Oracle vs. Sybase 38
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3
9 MISCELLANEOUS MIGRATION ASPECTS
9.1 Cursors A main difference between Oracle and Sybase ASE is on how the systems handle query results. In Sybase ASE, result sets are handles using „set processing‟, meaning that in a stored procedure result sets are typically stored in temporary tables and then further refined, whereas Oracle is based on cursor processing navigating through result sets. The underlying reason is that Oracle maintains the versioning of its transactions and guarantees data integrity through cursors. By using insensitive cursors in Sybase ASE, the same effect for the cursor result set is closest Oracle‟s cursor implementation. Both Oracle and Sybase ASE support cursors, with some –mostly small- differences in syntax and semantics. Oracle PL/SQL is implemented with an implicit cursor deallocation process. When you close an Oracle cursor, it gets automatically deallocated. Sybase ASE requires an explicit deallocate cursor statement to do so.
"REF CURSOR" is an Oracle datatype. Parameters and variables can be created with this datatype (called "cursor variables"). A cursor variable acts as a pointer to a result set, and can be associated with different queries at run-time and passed around between stored procedures, functions etc. Thus a cursor variable can be opened in one stored procedure, and the results fetched in another stored procedure, whereby the cursor variable is passed between both procedures. Since ASE does not have the REF CURSOR concept, PL/SQL using REF CURSOR needs to be rewritten, for example by rewriting all stored procedures involved, or by putting query results in (temporary) tables and let the different stored procedures access these.
9.2 Sequences Sybase ASE does not have a full equivalent of Oracle Sequences, but in most cases similar functionality can be achieved by using either an ASE identity column or a key counter table. A main criterium is whether the sequence values must be transactional (i.e. the sequence-generated value is rolled back when the enclosing transaction rolls back). If such transactionality is required, a key counter table must be used. If this is not required, then an identity column can be used.
Oracle code: CREATE SEQUENCE test_seq MINVALUE 1 STARTWITH 1 INCREMENTED by 1 CACHE 20;
INSERT INTO m_table VALUES (test_seq.nextval,…);
Equivalent Sybase ASE code with identity column: -- this example uses an int as the sequence counter. Use numeric or bigint as needed. CREATE PROCEDURE init_seq_nr (@seqtab varchar(30), @startwith int=1, @cache int=100) AS BEGIN set nocount on DECLARE @s varchar(100), @v int if object_id('seqtab') is not null begin set @s = 'drop table seqtab' exec (@s) end set @s = 'create table ' + @seqtab + '(seq int identity) with identity_gap = ' + convert(varchar, @cache)
Miscellaneous migration aspects 39
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3
EXEC (@s) if @startwith > 1 begin select @v = convert(int, reserve_identity (@seqtab, @startwith - 1)) end end go -- you can use either the output parameter or the return value, -- though the return value can only be an 'int' datatype -- NB: the values generated here are not transactional (they cannot be rolled back) CREATE PROCEDURE get_seq_nr (@seqtab varchar(30), @incremented_by int, @v_out int output) AS BEGIN set nocount on DECLARE @s varchar(100), @v int set @v = convert(int, reserve_identity (@seqtab, @incremented_by)) set @v_out = @v return @v end go
-- Initialize the sequence table EXEC init_seq_nr 'myseqtab', 1, 20 go
-- Now get the next sequence number -- you can use either the output parameter or the return value, -- though the return value can only be an 'int' datatype -- NB: the values generated here are not transactional (they cannot be rolled back) -- variant 1: use output parameter DECLARE @p_out int EXEC get_seq_nr 'myseqtab', 1, @p_out output INSERT INTO my_table VALUES (@p_out,…) go -- variant 2: use return value DECLARE @ret int DECLARE @p_notused int EXEC @ret = get_seq_nr 'myseqtab', 1, @p_notused INSERT INTO my_table VALUES (@ret,…) go Equivalent Sybase ASE code with key counter table: -- create table CREATE TABLE my_seq (seq int) go
-- initialize the sequence INSERT INTO my_seq select 0 go
-- create stored procedure to increment and return the value –- note that this can also be done with an OUTPUT parameter CREATE PROCEDURE get_seq (@incr int) AS UPDATE my_seq SET seq = seq + @incr SELECT @seq = seq FROM my_seq RETURN @seq go
-- execute the procedure to get the next sequence number DECLARE @seq int
Miscellaneous migration aspects 40
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3
EXEC @seq = get_seq 1 INSERT INTO m_table VALUES (@seq,…) go
Notes: When using a step count > 1 in ORacle (= 'incremented by' > 1), the ASE configuration parameter 'identity reservation size' must be set to the maximum block size (with sp_configure) The Oracle sequence attributes 'cycle', 'minvalue', 'maxvalue' and 'noorder' are not easy to support in ASE. To implement 'cycle', the identity counter can be set backwards with sp_chgattribute ..., 'identity_burn_max'. Yet another approach is to replace the sequence functionality with a static Java function which is visible across all processes (i.e. loaded by the system ClassLoader). This is not discussed further in this Guide.
9.3 Error/Exception handling In Oracle, each SQL statement is automatically checked for errors before proceeding with the next statement. If an error occurs, control immediately jumps to an exception handler if one exists. PL/SQL supports the creation of custom exception handlers to deal with different types of errors. Sybase ASE passes the control from one SQL statement to another without checking for errors. This means that in Sybase ASE, error checks must be performed after every SQL statement. The Oracle built-in procedure RAISE_APPLICATION_ERROR notifies the client of the server error condition and returns immediately to the calling routine. Oracle places an implicit SAVEPOINT at the beginning of a procedure. The built-in RAISE_APPLICATION_ERROR procedure rolls back to this SAVEPOINT or to the last committed transaction within the procedure. Control is then returned to the calling routine. Sybase ASE‟s equivalent to Oracle‟s RAISE_APPLICATION_ERROR is called RAISERROR. Unlike Oracle, RAISERROR does not return the controls to the calling routine. The first step in the conversion is to replace all RAISE_APPLICATION_ERROR calls with RAISERROR calls, followed immediately with a RETURN statement to emulate the Oracle exception handling. The second step is to handle the implicit SAVEPOINTs that Oracle creates at the beginning of each procedure. If the transaction is within one procedure this is relatively simple. But if the code uses nested stored procedures this becomes more complex and may require additional flow-control logic.
9.4 Outer join limitations Sybase ASE does not allow another join relationship on a table that already has an outer join (see example #1 below). In addition, for a query with an outer join and a qualification on a column from the inner table of the outer join, the results may be different than expected (example #2). Ideally, the database design should be de-normalized to remove the need for these relationships. It is generally recommended to use the ANSI outer join syntax in Sybase ASE rather than the T- SQL style syntax (*=. =*). Oracle Sybase ASE Example #1: Example #1: SELECT DISTINCT a.id, b.name, c.desc SELECT a.id, b.name, c.desc FROM a, b, c FROM a, b, c WHERE a.id = b.id (+) WHERE a.id = b.id and b.id2 = c.id2 (+) ( or b.id = c.id2 ) and b.id2 *= c.id2 and a.code = 1 and a.code = 1 ORDER BY b.name UNION SELECT a.id, '', '' FROM a WHERE a.code = 1 and ( NOT EXISTS ( SELECT 'X' FROM b WHERE a.id = b.id )) ORDER BY 2 Example #2: Example #2: SELECT a.id, b.name SELECT a.id, b.name
Miscellaneous migration aspects 41
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3
Oracle Sybase ASE FROM a, b FROM a, b WHERE a.id = b.id (+) WHERE a.id *= b.id AND b.name LIKE 'Bill%' AND b.name LIKE 'Bill%'
9.5 Migrating JDBC/ODBC/… Applications The data and any SQL code that are stored in the database (e.g., stored procedures and triggers) are migrated with the steps in Section 5. This section describes the following different types of client database applications that need to be migrated from Oracle to Sybase ASE. Embedded SQL application ODBC client application JDBC client application Database-specific library application C Applications Oracle forms In all cases, conversion of one type of application to any of the other types of applications is possible. For example, instead of converting your Oracle Embedded SQL application to a Sybase Embedded SQL application, you can convert your Oracle Embedded SQL application to a JDBC client application.
9.5.1 JDBC Migrating JDBC connections from Oracle to Sybase requires understanding how Oracle manages JDBC drivers vs. Sybase ASE. This will determine your approach on how to migrate JDBC. Oracle provides the following JDBC drivers: Thin driver: a pure Java driver used on the client-side, without an Oracle client installation. It can be used with both applets and applications. Oracle Call Interface (OCI) driver: used on the client-side with an Oracle client installation. It can be used only with applications. Oracle recommends the use of its Thin JDBC driver in all and any cases when connections are made through TCP/IP. Sybase ASE provides its own JDBC driver, named jConnect.
9.6 Oracle Forms Oracle Forms, a component of the Oracle Developer Suite, is Oracle's approach to design and build enterprise applications quickly and efficiently. Oracle Forms-based applications can retrieve and manipulate data in Oracle databases. Applications developed with Oracle Forms are unlikely to run well, or run at all, against Sybase ASE. Sybase PowerBuilder is an enterprise development tool that allows you to build many types of applications and components. It is one of a group of Sybase products that together provide the tools to develop client/server, multi-tier, and Internet applications. Oracle Forms applications can be rewritten using PowerBuilder. Most of the functionality provided by Oracle forms can be also be created by using PowerBuilder with Sybase ASE. Migration of Oracle Forms application to PowerBuilder application is not straightforward. The "form" is the basis of user interface (UI) in Oracle Forms while the "datawindow" is the basis of UI in PowerBuilder. Both are graphical in nature and are used to present data and accept user input. Both can contain elements graphical and non-graphical in nature. For more information on PowerBuilder, see http://www.sybase.com/powerbuilder .
Miscellaneous migration aspects 42
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3
10 DBA TASKS CROSS-REFERENCE This chapter seeks to provide some starting points with respect to mapping DBA tasks and concepts in Oracle to their equivalent in ASE. However, the tools and methods used for database administration and monitoring are very different as these are highly specific to each database brand. This makes it impossible to provide more than a loose mapping. For a successful migration, availability of sufficient DBA skills will be important.
Description Oracle Sybase ASE
Home Directory $ORACLE_HOME $SYBASE
Default Database/Instance $ORACLE_SID $DSQUERY
Command-line tool for SQL SQL*Plus in isql in $SYBASE/OCS- $ORACLE_HOME/bin/sqlplus 15_x/bin/isql
Import/export data imp / exp command or impdp For data import and export: /expdp command for data pump bcp command located in located in $ORACLE_HOME/bin $SYBASE/OCS-15_x/bin Oracle imports and exports the data For the definition import and and the DDL definitions, plus all other export: objects like type definitions, indexes, procedure and views. defncopy command in $SYBASE/OCS-15_x/bin Data exported with exp can only be imported with imp. To reverse engineering the DDL to be recreated in another environment: ddlgen command in $SYBASE/ASEP/bin
SQL*Loader is Oracle‟s high-speed Loading data from external files bcp command located in loader. It loads data into Oracle very $SYBASE/OCS-15_x/bin fast, but it cannot unloading Oracle database data into files. (bcp can also unload data into files)
Create a new database dbca command in Sybase Central or SQL command $ORACLE_HOME/bin create database
Create new network connection netca command in dsedit in $SYBASE/OCS- $ORACLE_HOME/bin 15_x/bin
DBA Tasks Cross-Reference 43
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3
Description Oracle Sybase ASE
Setup new Oracle Enterprise emca command in Sybase Central in combination with Manager (OEM) server $ORACLE_HOME/bin Sybase Control Center is equivalent to OEM. Setup Sybase Central: installed automatically when Sybase ASE is installed. Installs as part of the client installation. Setup Sybase Control Center: Install the software with the supplied Sybase Installer.
Load data into the database SQL*LOADER in bcp command located in $ORACLE_HOME/bin/sqlldr $SYBASE/OCS-15_x/bin using bcp in
Start database server Manual: startserver command in Start SQL*Plus as sysdba $SYBASE/ASE- 15_x/install SQL> STARTUP startserver –f Starts the instance, , mounts the RUN_$DSQUERY database and opens the database. The RUN_$DSQUERY file is the Script: spfile equivalent. dbstart command in $ORACLE_HOME/bin Both commands are using the spfiles located in $ORACLE_HOME/dbs in the following order: 1. spfile$ORACLE_SID.ora 2. spfile.ora 3. init$ORACLE_SID.ora
Start backup server N/A startserver command in $SYBASE/ASE- 15_x/install startserver –f RUN_$DSQUERY_BS The RUN_$DSQUERY_BS file contains the startup parameters.
Start monitor server emctl command in startserver command in $ORACLE_HOME/bin $SYBASE/ASE- 15_x/install emctl start dbconsole startserver –f RUN_$DSQUERY_MS The RUN_$DSQUERY_MS file contains the startup parameters.
DBA Tasks Cross-Reference 44
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3
Description Oracle Sybase ASE
Show running processes Unix: showserver command in ps –aef | grep $SYBASE/ASE- $ORACLE_SID 15_x/install Windows: pslist –d oracle
Stop database server Login to SQL*Plus and execute: Login via isql and execute the command: SQL>shutdown shutdown For normal shut down go SQL>shutdown immediate; Without parameters the server will For immediate shut down wait for all transactions to finish. Adding „with nowait‟ will terminate SQL>shutdown abort; all sessions and shut down the For emergency shut down server immediately.
Stop backup server Oracle does not have a concept of a Login via isql into the Sybase ASE Backup Server. database server and execute the command: shutdown Backup_Server_name go By default this waits for all current backups to finish. Adding „with nowait‟ will terminate all sessions and shut down the backup server immediately.
DBA Tasks Cross-Reference 45
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3
Description Oracle Sybase ASE
Oracle has the following ways of Sybase ASE always performs a hot Database Backup performing a database backup: backup; this requires hardly any configuration. This is the same imp / exp commands: this can functionality as Oracle‟s Archive import/export the entire database Log backup, but no archive file (including all data), individual cleanup is necessary. schemas or a single table. The command dump database Data Pump: new import / export backs up an entire database (full feature since Oracle 10g. The basic dump); dump transaction functionality is identical to the old only backs up the transaction log imp exp and commands, but since the previous dump Data Pump is faster. (incremental backup). RMAN: The Oracle Recovery The command load database Manager (RMAN), command-line restores a full backup; load as well as Enterprise Manager- transaction loads an based, is the Oracle-preferred incremental backup following loads method of efficiently backing up of earlier backups. and restoring an Oracle database. For these dump/load commands, Various backup options exist, Backup Server must be running. some of which require the Oracle database to be shut down first.
Oracle dynamic performance views MDA tables Information about system performance
Oracle static data dictionary views System tables (catalogs) and system Information about schema stored procedures (sp_*)
DBA Tasks Cross-Reference 46
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3
11 ORACLE-TO-SYBASE MIGRATION CROSS-REFERENCE This chapter provides specific suggestions on how to migrate a Oracle feature to Sybase ASE. This cross-reference is an extended version of the Oracle checklist in chapter 3. Much of this type of conversion can in principle be done using a text editor with search-and-replace commands, or with tools like 'sed'.
11.1 Oracle-to-Sybase ASE migration: category "Simple Conversion"
Oracle Sybase ASE ("simple conversion")
Connecting to an Oracle schema Connecting to a Sybase database; also see section 4.5
CONNECT user_name/password USE database_name SET ROLE
The Oracle SQL*Plus “slash” character sends preceding Equivalent to the ISQL go command at the end of a PL/SQL text to the Oracle server. batch of SQL statements / go
The semicolon is a statement delimiter in PL/SQL No statement delimiters; remove Oracle delimiter ; semicolons
The Oracle DUAL table Should be removed completely from queries in Sybase ASE; but if it occurs many times in Oracle queries, it SELECT sysdate FROM DUAL may also be created as a dummy table in ASE; see section 4.10
SET SAVEPOINT savepoint-name SAVE TRAN[SACTION] savepoint-name
Variable/Parameter declarations; naming syntax In Sybase ASE, variable/parameter names must start with the character @. In ASE, the maximum length is 30 bytes; in Oracle, longer names are allowed. DECLARE count NUMBER DECLARE @count INT
Assign default value in variable declaration Explicitly assign value after variable declaration
DECLARE blood_type char(2) := 'O'; DECLARE @blood_type CHAR(2) SET @blood_type = 'O'
Multiple variable declarations with a single DECLARE When declaring multiple variables with one keyword DECLARE keyword, the variables must be comma- separated ASE. Cursors must be declared separately DECLARE with DECLARE…CURSOR V1 NUMBER(10,0); V2 CHAR(20); DECLARE @v1 int, CURSOR mycursor IS @v2 char(20) SELECT * FROM mytable;
Oracle-to-Sybase Migration Cross-Reference 47
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3
Oracle Sybase ASE ("simple conversion")
Declarations without DECLARE keyword in declaration DECLARE keyword is required in Sybase ASE. section of stored procedures/functions Cursors must be declared separately with DECLARE…CURSOR CREATE PROCEDURE p AS CREATE PROCEDURE p V1 NUMBER(10,0); AS V2 CHAR(20); BEGIN CURSOR mycursor IS DECLARE SELECT * FROM mytable; @v1 int, BEGIN @v2 char(20) …statements… END; DECLARE mycurs CURSOR AS SELECT * FROM mytable …statements… END go
Variable assignment SET @myvar = expression myvar := expression; SELECT @myvar = expression
Transferring table data into a variable Directly select into the variable
SELECT my_col INTO my_variable SELECT @my_variable = my_col FROM FROM my_table WHERE id = 123; my_table WHERE id = 123
Constants Redefine as variables and check scope of usage (local or global).
%TYPE denotes the datatype of a column in an existing Explicitly declare the variable with the column's actual table datatype
DECLARE count my_table.id%TYPE
Dynamic SQL Use Sybase ASE execute-immediate
EXECUTE IMMEDIATE '…sql…'; SET @cmd = '…sql…' EXECUTE (@cmd) or: EXECUTE ('…sql…')
Optional clauses: EXECUTE IMMEDIATE '…sql…' USING …; With the clauses USING (specifies parameters to the EXECUTE IMMEDIATE '…sql…' INTO …; dynamic SQL), INTO (puts results into variables for EXECUTE IMMEDIATE '…sql…' BULK COLLECT single-row results), BULK COLLECT INTO (stores INTO …; results into Oracle collections), the query should be rewritten to achieve the same effect in ASE.
Oracle-to-Sybase Migration Cross-Reference 48
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3
Oracle Sybase ASE ("simple conversion")
Loops with LOOP/END LOOP: Convert to WHILE-loops. Oracle's EXIT and CONTINUE corresponds to ASE's BREAK and LOOP CONTINUE though ASE cannot have a condition …statements…; associated with these statements. EXIT [WHEN …condition…]; /*exit loop*/ …statements…; WHILE 1=1 /* back to top for next iteration: */ BEGIN CONTINUE [WHEN …condition…]; …sql… …statements…; …conditional exit… END LOOP; END
Or:
WHILE
FOR loops Convert to WHILE; use variables to implement FOR
FOR i IN 1..5 DECLARE @i int, @i_start int, @i_end LOOP int …statements… SET @i_start = 1, @i_end = 5 END LOOP; SET @i = @i_start WHILE @i <= @i_end BEGIN …statements… SELECT @i = @i + 1 END
CURSOR loops Convert to an ASE cursor
DECLARE CURSOR c IS …select-statement…;
LOOP myvariable IN c …statements… END LOOP;
GOTO statement and labels Change label syntax from <
Oracle-to-Sybase Migration Cross-Reference 49
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3
Oracle Sybase ASE ("simple conversion")
Oracle Outer join syntax Translates to Sybase ASE T-SQL outer join syntax or to ANSI outer join syntax (preferred). Some restrictions apply in Sybase, see section 9.4.
// right outer join SELECT * FROM t1, t2 SELECT * FROM t1, t2 WHERE t1.col1 =* t2.col2 (T-SQL WHERE t1.col1 = t2.col2(+) syntax)
SELECT * FROM t1 RIGHT [OUTER] JOIN t2 ON t1.col1 = t2.col2 (ANSI syntax)
// left outer join SELECT * FROM t1, t2 SELECT * FROM t1, t2 WHERE t1.col1(+) = t2.col2 WHERE t1.col1 *= t2.col2 (T-SQL syntax)
SELECT * FROM t1 LEFT [OUTER] JOIN t2 ON t1.col1 = t2.col2 (ANSI syntax)
SET TRANSACTION READ WRITE Remove in Sybase ASE; see chapter 8
ALTER TABLE mytable TRUNCATE PARTITION Replace by TRUNCATE TABLE mytable partition_name PARTITION partition_name
CREATE OR REPLACE PROCEDURE (or Replace by DROP PROCEDURE (or FUNCTION) FUNCTION) followed by CREATE PROCEDURE (or FUNCTION)
ALTER PROCEDURE (or FUNCTION) Replace by DROP PROCEDURE (or FUNCTION) followed by CREATE PROCEDURE (or FUNCTION)
CREATE PROCEDURE… IS… Change to CREATE PROCEDURE… AS…
Stored procedure OUT/IN OUT parameters Sybase ASE supports input and input+output parameters, but no output-only parameters. In addition, the output keyword must be specified when CREATE PROCEDURE p calling the procedure (a IN number, b OUT number, c IN OUT number) IS … CREATE PROCEDURE p @a int, @b int output, @c int output AS …
EXEC p @var1, @var2 output, @var3 output
Stored procedure execution with named parameters Convert to ASE syntax with named parameters: (param => value) EXEC @result = proc_name @param1 = @my_var, result := proc_name(param1 => my_var, param2 @param2 = 123 => 123);
Oracle-to-Sybase Migration Cross-Reference 50
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3
Oracle Sybase ASE ("simple conversion")
Stored procedure execution with positional parameters Convert to ASE syntax with named parameters: (:var) declare @a int, VAR a NUMBER; @b int, VAR b NUMBER; @c int, VAR c NUMBER; @return_status
EXEC proc_name (:a, :b, :c) EXEC @return_status = proc_name @a, @b, @c
Procedure execution In ASE, the EXEC[UTE] keyword is mandatory In Oracle, the EXEC[UTE] keyword is not used (except when the procedure is the first statement in the batch) CREATE PROCEDURE p1 AS CREATE PROCEDURE p1 BEGIN AS …statements… BEGIN END; …statements… END CREATE PROCEDURE p2 go AS BEGIN CREATE PROCEDURE p2 p1; AS END; BEGIN EXECUTE p1 END go
SQL Function declaration with DETERMINISTIC In Sybase ASE, remove DETERMINISTIC keyword
CREATE FUNCTION f_func (p NUMBER) RETURN NUMBER DETERMINISTIC IS…
Execution of a SQL Function In Sybase ASE, the name of the executed SQL function must always be preceded by the owner's name
select myfunc(123); select dbo.myfunc(123) select jsmith.yourfunc(456)
DECLARE CURSOR cursor-name IS… Change to DECLARE cursor-name INSENSITIVE CURSOR AS… ASE's insensitive cursor is closest to Oracle's cursor implementation
Oracle cursors Oracle cursors are automatically deallocated when closed. ASE cursors must be deallocated explicitly with DEALLOCATE CURSOR cursor-name. This should be added after every cursor CLOSE.
Cursor Attribute %ISOPEN No equivalent in ASE, remove .
Cursor Attributes %FOUND, %NOTFOUND Convert to using @@sqlstatus
Cursor Attribute %ROWCOUNT Convert to using @@rowcount
Oracle-to-Sybase Migration Cross-Reference 51
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3
Oracle Sybase ASE ("simple conversion")
AFTER triggers (on statement level) Similar to Sybase ASE table triggers
INSTEAD OF triggers (on views) Similar to Sybase ASE INSTEAD-OF triggers
SQL%ROWCOUNT Replace by @@rowcount Indicates the number of rows affected by the most DECLARE @rc INT, @err INT recently executed PL/SQL statement SELECT * FROM mytable WHERE id = 1234 SELECT * FROM mytable WHERE id = 1234; SELECT @rc = @@rowcount, @err = @@error IF SQL%ROWCOUNT = 0 THEN IF @rc = 0 DBMS_OUTPUT.PUT_LINE('No rows print 'No rows found.' found.'); END IF;
BOOLEAN datatype (for PL/SQL variables only) Convert to variables of type BIT (allows only 0 and 1; NULL = 0) or TINYINT NULL. Decide on a Allowed values are TRUE, FALSE and NULL. standard encoding like 0=false; 1=true. Instead of using the numeric literals 0 and 1 in tests and assignments, two variables named @true and @false could be defined (and set to 1 and 0), so as to use these names instead.
MERGE statement Migrate to ASE 15.7, which supports MERGE
Partitioned tables with composite partitioning ASE supports partitioned tables, but no composite partitioning. Remove the SUBPARTITION clause. CREATE TABLE mytable (...columns...) PARTITION BY RANGE(ptn_key_col) SUBPARTITION BY HASH(subptn_key_col) [...]
Performance-optimized native PL/SQL datatypes (for Convert to INTEGER, DOUBLE, FLOAT datatypes PL/SQL variables only)
BINARY_INTEGER BINARY_DOUBLE BINARY_FLOAT
IF-THEN-ELSE In Sybase ASE, there is no THEN or END IF, so remove them IF expression THEN IF expression statement; statement ELSE ELSE statement; statement END IF;
Oracle-to-Sybase Migration Cross-Reference 52
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3
Oracle Sybase ASE ("simple conversion")
Multiple statements in an IF-THEN-ELSE branch In Sybase ASE, there can be only a single statement expression in each branch; multiple statements must IF expression be grouped in a BEGIN- END block. THEN statement; IF expression statement; BEGIN ELSE statement statement; statement statement; END END IF; ELSE BEGIN statement statement END
Conditional test based on EXISTS subquery Can be kept identical in ASE, but this can also be simplified greatly in ASE: DECLARE v_x NUMBER(10,0); DECLARE @x int v_temp NUMBER(1, 0) := 0; SET @x = 0 IF EXISTS ( …subquery… ) SELECT 1 INTO v_temp SET @x = -1 FROM DUAL END WHERE EXISTS ( …subquery… );
IF v_temp = 1 THEN v_x := -1;
String concatenation operator: || Sybase ASE supports + as the string concatenation operator; it also supports || though this is formally undocumented. userenv('sessionid') Equivalent to session-specific global variable @@spid (since @@spid values are re-used, the sysprocesses.kpid value can also be used to create a better uniqueness)
MOD(X,Y) X % Y
CEIL() CEILING()
TRUNC(number) CONVERT(INT,..)
SUBSTR() SUBSTRING()
SUBSTR() function with two parameters Rewrite with the length of the expression as the 3rd parameter
SELECT substr('John', 2) returns 'ohn' SELECT substring ('John', 2, len('John'))
LENGTH() CHAR_LENGTH() or LEN() or DATALENGTH()
CHR() CHAR()
REPLACE() STR_REPLACE()
Oracle-to-Sybase Migration Cross-Reference 53
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3
Oracle Sybase ASE ("simple conversion")
TO_CHAR(expression) CONVERT(VARCHAR(n), expression)
TO_CHAR(expression, datepart) Convert to use the ASE datepart() function
TO_CHAR(sysdate, 'dd') CONVERT(VARCHAR,datepart(dd,getdate()))
TO_CHAR(expression, format-string) Implement the formatting explicitly with ASE functions TO_CHAR(some-number, '999D99') TO_CHAR(some-number, '999') CONVERT(VARCHAR,ROUND(some-number,2)) CONVERT(VARCHAR,CONVERT(INT,some- number))
TO_NUMBER(expression) CONVERT([BIG|SMALL|TINY]INT, expression) CONVERT(NUMERIC(n,m), expression)
Date/time functions and calculations Rewrite with ASE date/time functions like DATEADD(), DATEDIFF(), DATEPART(), DATENAME()
SELECT add_months( xyz ,3 ) FROM dual SELECT DATEADD(month, 3, xyz)
SELECT nr_days := DateEnd - DateStart SELECT @nr_days = datediff(dd, DateStart, DateEnd)
SYSDATE, SYSTIMESTAMP Replace by CURRENT_BIGDATETIME()
TRUNC(date/time [,unit]) Replace by CONVERT() with the date/time formatting styles
LAST_DAY() Last day of a month function based on a date value; rewrite using ASE SQL functions
NVL() function Replace by ISNULL() function
NVL(a,b) ISNULL(a,b)
Inconsistent use of upper/lowercase for identifiers Either use a case-insensitive sort order in ASE, or use (Oracle is case-insensitive for identifiers) consistent upper/lowercase spelling for identifiers (see section 5.2)
Identifiers that are Sybase ASE reserved words (see Change such identifiers so that they are not a reserved section 4.8) word.
INSTR() function with two parameters Replace by charindex()
SELECT INSTR('abcabc', 'ab') SELECT CHARINDEX('abcabc', 'ab')
Oracle-to-Sybase Migration Cross-Reference 54
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3
Oracle Sybase ASE ("simple conversion")
Derived tables (also known as "inline views") without ASE always requires a correlation name for a derived correlation name table select a select a from (select b as a, d as b from mytab) from (select b as a, d as b from mytab) where b > 0 [as] somename where b > 0
ALTER TABLE … SPLIT PARTITION… Migrate to ASE 15.7 ESD#2 which supports these ALTER TABLE … MERGE PARTITIONS… statements.
Quoted identifiers. Oracle allows using quoted identifiers Sybase ASE also allows quoted identifiers delimited by by enclosing an identifier in double quotes. Quoted double quotes, but this is disabled by default. To use identifiers are case-sensitive, unlike unquoted identifiers quoted identifiers, the command set which are case-insensitive. quoted_identifiers on must be executed first. This command affects only the session executing it. CREATE TABLE "mytable" ("mycol" NUMBER);
Ignore quotes for all-uppercase quoted identifiers. Note that all-uppercase quoted identifiers do not need to be quoted: "MYTABLE" (quoted) is identical to MYTABLE (without quotes) in Oracle.
Oracle hints; indicated by a special comment directly Remove all Oracle hints following the SELECT:
SELECT /*+ INDEX (C) */ NAME FROM CUSTOMERS C WHERE ZIPCODE = 54321
Hint keywords: ALL_ROWS CURSOR_SHARING_EXACT NOAPPEND APPEND DRIVING_SITE NOCACHE CACHE DYNAMIC_SAMPLING NOPARALLEL CLUSTER MODEL_MIN_ANALYSIS NOREWRITE FACT NATIVE_FULL_OUTER_JOIN OPT_PARAM FIRST_ROWS NO_NATIVE_FULL_OUTER_JOIN ORDERED FULL NO_PARALLEL PARALLEL HASH NO_PARALLEL_INDEX PARALLEL_INDEX INDEX NO_PUSH_PRED PQ_DISTRIBUTE INDEX_ASC NO_PUSH_SUBQ PUSH_PRED INDEX_DESC NO_PX_JOIN_FILTER PUSH_SUBQ INDEX_FFS NO_QUERY_TRANSFORMATION PX_JOIN_FILTER INDEX_JOIN NO_RESULT_CACHE QB_NAME INDEX_SS NO_REWRITE RESULT_CACHE LEADING NO_STAR_TRANSFORMATION INDEX_COMBINE MERGE NO_UNNEST INDEX_SS_ASC MONITOR NO_USE_HASH INDEX_SS_DESC NO_EXPAND NO_USE_MERGE NO_INDEX_FFS NO_FACT NO_USE_NL NO_INDEX_SS NO_INDEX NO_XML_QUERY_REWRITE NO_MERGE REWRITE NO_XMLINDEX_REWRITE NO_MONITOR UNNEST STAR_TRANSFORMATION USE_HASH USE_CONCAT USE_NL_WITH_INDEX USE_MERGE NOPARALLEL_INDEX USE_NL
Oracle-to-Sybase Migration Cross-Reference 55
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3
11.2 Oracle-to-Sybase ASE migration: category "Partial Rewrite" For the Oracle features listed below, migration to partly equivalent Sybase ASE features is possible, although potentially significant syntax changes and possibly partial rewriting of algorithms may be required.
Oracle Sybase ASE ("partial rewrite")
Database links Equivalent to ASE proxy tables, mapping to a remote table CREATE DATABASE LINK SALES.PROD [ CONNECT TO CURRENT_USER ] using create proxy_table sales_proxy 'SALES'; at SALES.salesdb..salesdata
SELECT * FROM salesdata@SALES; select * from your_proxy
External tables Equivalent to ASE proxy tables, mapping to an O/S file create table my_external_tab ( ...columns...) create proxy_table my_external_tab organization external ( ...columns...) ( default directory external_data_dir external file at '...pathname...' access parameters column delimiter ',' ( records delimited by newline fields terminated by ',' location ('...pathname...') )
Sequences In some cases, this can be replaced by using ASE Generate unique numbers, for example for primary identity columns. In other cases, the sequence keys functionality must be emulated with a key counter table and a stored procedure. See section 9.2.
Table-valued User-defined SQL Functions ASE only supports scalar User-defined SQL functions. Rewrite with temporary tables.
Pipelined Table Functions ( a special case of Table- Rewrite with cursors or with an ASE proxy table valued User-defined SQL Functions) mapping to a stored procedure (though the performance of Oracle Pipelined Table Functions can FUNCTION my_func probably not be achieved) RETURN my_out_tab PIPELINED;
Synonyms For synonyms for tables or views, replace by an ASE view; for table/view synonyms at dblinks, replace by an ASE proxy table. For synonyms for stored procedures or functions, replace by a wrapper stored procedure/function; for stored procedure synonyms at dblinks, replace by a remote procedure call. For other synonyms, application changes are required.
Comments on database objects No direct equivalent. An method for storing object comments in ASE is described COMMENT ON TABLE mytab IS "This is my table"; in http://www.sybase.com/detail?id=607
Oracle-to-Sybase Migration Cross-Reference 56
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3
Oracle Sybase ASE ("partial rewrite")
Bitmap indexes ASE does not support bitmap indexes. Remove BITMAP and create a regular index. CREATE BITMAP INDEX my_ix ON mytable(…) Sybase IQ supports bitmapped indexes.
Temporary tables Replace by ASE temporary tables whose names start with the # character:
CREATE GLOBAL TEMPORARY TABLE temptab CREATE TABLE #temptab […] […] [ON COMMIT {PRESERVE|DELETE} ROWS] SELECT * INTO #temptab FROM my_table
Note that there are differences in scope between an Oracle temporary table and a Sybase #temporary table: an Oracle temporary table is visible by all users (though a user can only see his own data rows in the table) whereas a Sybase #temp table is visible only to the session that created it. In addition, an Oracle temporary table is a permanent table that must be dropped explicitly (only the data in the Oracle temporary table is automatically deleted); a Sybase #temp table is automatically dropped at the end of the procedure or session that created it.
IS TABLE OF or AS VARRAY(n)OF Rewrite algorithm with a temporary table and use define a PL/SQL "table" (= non-database table, array). FETCH or SELECT to process rows. Alternatively, Also known as a "collection" (various types of Oracle convert the table to a Java object with different data collections exist). elements, which can be stored in a table column.
Oracle-to-Sybase Migration Cross-Reference 57
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3
Oracle Sybase ASE ("partial rewrite")
Nested tables Change to use a separate table for the nested table in Allow a column to be defined as a table, that can hold the column, with a primary key-foreign key N rows (=N column values) relationship. Also known as a "collection" (various types of Oracle collections exist).
CREATE TYPE address_t AS OBJECT ( street VARCHAR2(30), city VARCHAR2(20), state CHAR(2), zip CHAR(10), country CHAR(30));
CREATE TYPE address_tab IS TABLE OF address_t;
CREATE TABLE customers ( custid NUMBER, address address_tab ) NESTED TABLE address STORE AS customer_addresses;
INSERT INTO customers VALUES (654, address_tab(address_t('148 Oak Drive', 'Dallas', 'TX', '75240', 'USA'), address_t('561 Virginia Road', 'Concord', 'MA', '01742', 'USA')));
NB: customer_addresses is an object table as well as a nested table at the same time.
Object tables Either replace with regular tables and columns, or use a Java class to define a column as a complex datatype CREATE TYPE person_type AS OBJECT ( containing different fields. name VARCHAR2(30), address VARCHAR2(100));
CREATE TABLE person_obj_table OF person_type;
%ROWTYPE declares a PL/SQL record with the Declare each field as an individual variable and modify same columns as a particular table all references accordingly. Alternatively, convert the record to a Java object with different data elements, DECLARE cust customer%ROWTYPE which can be stored in a table column.
Define a PL/SQL record type by enumerating the Declare each field as an individual variable and modify fields with IS RECORD OF or TYPE…IS RECORD all references accordingly. Alternatively, convert the record to a Java object with is treated as an array.
Non-integer RETURN value in stored procedure Sybase ASE stored procedures can only return an integer value. Oracle stored procedures can return a scalar value of When a different datatypes is returned, rewrite by any datatype. using an output parameter or rewrite with a SQL function
Oracle-to-Sybase Migration Cross-Reference 58
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3
Oracle Sybase ASE ("partial rewrite")
User-defined Packages Translate packages to the individual objects that the package consists of (stored procedures, data types, etc.)
Overloaded stored procedures Translate to a single stored procedures or split into (multiple procedures with identical names but different separate stored procedures parameter datatypes or different number of parameters)
PL/SQL Exception handling; defining exception Rewrite and perform checks on @@error and handlers @@rowcount after every SQL statement.
EXCEPTION WHEN ZERO_DIVIDE THEN -- handles 'division by zero' error […] EXCEPTION WHEN TOO_MANY_ROWS -- handle case that > 1 row affected […] EXCEPTION WHEN NO_DATA_FOUND -- handle case that no rows affected […] EXCEPTION WHEN DUP_VAL_ON_INDEX -- handle case for duplicate index key […] (etc… other conditions exist
SQLCODE, SQLERRM Replace SQLCODE by @@error. ASE has no equivalent of SQLERRM Indicates the error status and error message text of the most recently executed PL/SQL statement; used with DECLARE @rc INT, @err INT the exception handling section SELECT * FROM mytable WHERE id = 1234 EXCEPTION SELECT @rc = @@rowcount, @err = @@error WHEN OTHERS THEN IF @err = 0 error_code := SQLCODE; BEGIN error_msg := substr(SQLERRM, 1, 200); INSERT INTO audit_table(err_no,err_msg) INSERT INTO VALUES (@err, ''); audit_table(err_no,err_msg) END VALUES (error_code, error_msg); END;
RAISE_APPLICATION_ERROR Recode with Sybase ASE functions such as RAISERROR or PRINT immediately followed by a In stored procedures, this also rolls back until the RETURN in stored procedures implicit savepoint at the start of the procedure (or after the last committed transaction in the procedure)
Column Encryption Rewrite with ASE column encryption
LOB locators Migrate to ASE 15.7, which supports LOB Locators
Oracle-to-Sybase Migration Cross-Reference 59
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3
Oracle Sybase ASE ("partial rewrite")
Data compression Migrate to ASE 15.7, which supports data compression
Retrieving data to the client in stored procedures using DBMS_OUTPUT package
DBMS_OUTPUT.PUT_LINE Replace by direct SELECT or PRINT statements
DBMS_*, UTL_* package calls Recode with Sybase ASE features if possible, (excl. DBMS_OUTPUT) otherwise remove
SDO_* package calls Spatial data features, remove/recode
SQL*Loader (sqlldr) Rewrite using the Sybase bcp utility. Oracle‟s high-speed data loader utility (only loading, no unloading).
Materialized Views Migrate to ASE 15.7 ESD#2 which supports materialized views (a.k.a. "precomputed result sets").
Global variables (in a PL/SQL package) Global variables are not supported; either pass all variables around as parameters, or store such values in a table and read/update that table as needed. Alternatively, Java static classes can be used.
INTERSECT construct Rewrite as a join
SELECT a FROM tab1 WHERE b > 10 SELECT tab1.a FROM tab1, tab2 INTERSECT WHERE tab1.a = tab2.c SELECT c FROM tab2 WHERE d = 0 AND tab1.b > 10 AND tab2.d = 0
MINUS construct Rewrite with NOT IN (single column) or NOT EXISTS (multiple columns) SELECT a,b,c FROM tab1 WHERE … MINUS SELECT a,b,c FROM tab1 SELECT d,e,f FROM tab2 WHERE … WHERE NOT EXISTS (SELECT * from tab2 WHERE tab2.d = tab1.a AND tab2.e = tab1.b AND tab2.f = tab1.c)
Oracle-to-Sybase Migration Cross-Reference 60
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3
Oracle Sybase ASE ("partial rewrite")
Specific SQL clauses Replace by corresponding Sybase ASE functionality, if AS OF CROSS IGNORE available. Otherwise, rewriting the SQL is required. AS OF TIMESTAMP CUBE ITERATE CONNECT BY FOR NATURAL DIMENSION KEEP NULLS DIMENSION BY MAIN NULLS FIRST EXCLUDE MODEL NULLS LAST GROUPING SETS NAV ROLLUP INCLUDE NOCYCLE SIBLINGS MEASURES NOWAIT SINGLE RETURN ALL ROWS ON REFERENCE RETURN UPDATED ONLY LOCKED ROWS RULES START WITH PARTITION BY SAMPLE UNIQUE REFERENCE SEED UNPIVOT SYSTIMESTAMP SKIP WAIT
Capitalize first letter of all words in a string Rewrite with stored procedures or SQL functions INITCAP( string-expression )
INSTR() function with three or four parameters Create a SQL function to perform the advanced (3=start position, 4=nth occurrence) searches. Note that charindex() accepts a 3rd paramter in SELECT INSTR('abcabc', 'ab', 2) ASE 15.7, but this cannot have a negative value (for SELECT INSTR('abcabcabc', 'ab', 2, 2) backward search) as is allowed in Oracle
NVL2() function Convert to a CASE expression
SELECT NVL2(salary,salary*2, 123) FROM… SELECT CASE WHEN salary = NULL OR salary = '' THEN 123 ELSE salary * 2 END FROM…
DECODE() function Convert to a CASE expression Used to evaluate with „if-else‟ type logic
SELECT SELECT DECODE(T1.C1, 'ABC', case T1.C1 T1.C2, when 'ABC' then T2.C2 else T3.C3 T1.C3) as P_ID end as P_ID FROM T1 FROM T1
Primary key and foreign key with different datatypes, Unlike Oracle, ASE requires that a foreign key and different precision/scale (for numeric datatypes) or primary key have identical datatypes. Modify the different length (for character datatypes) datatypes accordingly.
Cluster (as created with CREATE CLUSTER) Change the data model to use individual tables; consider using views to avoid making changes to existing SQL code
Oracle-to-Sybase Migration Cross-Reference 61
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3
Oracle Sybase ASE ("partial rewrite")
VARCHAR2 variables longer than 16384 bytes The maximum length of string variables is 16384 bytes; rewrite code, either using shorter ASE varchar strings, or use ASSE LOB variables or LOB locators DECLARE msg VARCHAR2(32767) in ASE 15.7 (for columns, VARCHAR2 cannot be longer than 4000 bytes)
SQL functions where the last statement is not ASE requires that a SQL function has RETURN as its RETURN last statement. This may require some re-coding of the flow control.
Derived tables (also known as "inline views") using Rewrite with ASE derived table syntax "with" syntax
with x as (select b as a, d as b from mytab) select a from x where b > 0
UNIONs in cursors A cursor with a UNION cannot be updatable in ASE; such code may need to be rewritten.
PRAGMA directives Rewrite with ASE syntax/functionality.
Autonomous transactions ASE does not support autonomous transactions; (AUTONOMOUS_TRANSACTION) rewrite with ASE transactional semantics.
ON DELETE CASCADE constraints Rewrite with ASE triggers
XMLTYPE (XML data type) Rewrite with TEXT, IMAGE or VARCHAR XML functions extract(), existsnode(), xmlexists(), etc datatatypes and with ASE functions xmlextract(), xmltable(), etc.
ROWID A similar effect can be achieved by add an identity An Oracle table always contains a ROWID column column to each table, and name the column "ROWID". with a unique identifier for each row, even if no There can be only one identity column per table. If primary key was defined for the table. The ROWID can be referenced in queries. there is already an identity column for the primary key, for example to replace an Oracle sequence, add a SELECT last_name, ROWID virtual computed column named "ROWID", equal to INTO var_lname, var_rowid the identify column. This method can also be used FROM emp when existing Oracle code uses a different spelling, WHERE empid = 98765 like "rowid": CREATE TABLE mytab
(ROWID NUMERIC IDENTITY, rowid AS ROWID, …other columns…)
Oracle-to-Sybase Migration Cross-Reference 62
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3
Oracle Sybase ASE ("partial rewrite")
ROWNUM When the objective is to select the top N rows, this can be achieved with select top N …from… For each row returned by a query, the ROWNUM pseudocolumn returns a number indicating the order of When more complex selections are done (e.g. only get the row in the result set. This can be used in queries, rows 10-20) , the an identity column (which should for example to select only a subset of the result set. probably be named "ROWNUM") can be added to the result set with the identity() function, which
assigns a sequence number to every row in the result SELECT * FROM emp set. This column can then be used in queries. Note WHERE state = 'CA' that this requires one extra query step: AND ROWNUM > 9 AND ROWNUM < 21 ORDER BY last_name; SELECT *, ROWNUM=identity(int) INTO #t FROM emp WHERE state = 'CA' ORDER BY last_name SELECT
Oracle-to-Sybase Migration Cross-Reference 63
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3
11.3 Oracle-to-Sybase ASE migration: category "Major Rewrite" For the Oracle features listed below, no direct equivalent is available in Sybase ASE. Consequently, rewriting or redesigning algorithms or parts of applications will be required.
Oracle Sybase ASE ("major rewrite")
Oracle MVCC (Multi-Version Concurrency Control; No direct equivalent of MVCC. Some aspects may be "writers don‟t block readers, readers don't block addressed by using DATAROWS locking, using the writers") READPAST option., or running SELECT queries at Relevant aspects: isolation level 0 (READ UNCOMMITTED). For other cases, the application may need to be Applications or queries relying on non- modified, for example by keeping transactions as short blocking MVCC as possible. Long-running transactions See section 8 for details. DDL in transactions SET TRANSACTION READ ONLY SQL*Plus autocommit/commit-on-exit
SQL*Plus The Sybase ASE counterpart for SQL*Plus is the isql utility. SQL*Plus allows for more complex configuration settings and SQL*Plus-specific (i.e. non-PL/SQL) client-side commands inside SQL*Plus. Existing SQL*Plus-based functionality must be rewritten for ASE.
BEFORE triggers No direct equivalent. Some aspects of the functionality (like domain integrity) may be covered by rules or CHECK constraints at the table definition level; however an Oracle BEFORE trigger can perform far more complex processing than can be handled by rules or constraints. If this functionality cannot be implemented with Sybase ASE "after" triggers, the application may need to be changed to apply the functionality in a different way.
Triggers on row level (BEFORE and AFTER) No direct equivalent; some logic may be changed to operate on the ASE pseudo-tables inserted and deleted; otherwise, see BEFORE triggers above.
Multiple triggers for a DML type on a table No direct equivalent; if the functionality cannot be consolidated in a single ASE trigger, the application may need to be changed to apply the functionality in a different way.
Oracle-to-Sybase Migration Cross-Reference 64
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3
Oracle Sybase ASE ("major rewrite")
REF CURSOR No direct equivalent. In ASE, REF CURSORs need to be rewritten, for example by rewriting all stored procedures involved, or by putting query results in (temporary) tables and let the different stored procedures access these. Also see section 9.1.
Regular Expressions; functions REGEXP_LIKE(), No direct equivalent since ASEdoes not support REGEXP_SUBSTR(), REGEXP_REPLACE(), regular expressions.Rewrite with ASE SQL using REGEXP_INSTR() custom processing instead of RegEx
Windowing queries (SELECT…OVER(…) …) No equivalent in Sybase ASE. Rewrite with classic SELECT name, salary, ASE features, possibly requiring breaking up a query NTILE(4) OVER (ORDER BY salary DESC) in multiple steps. Alternatively. Use Sybase IQ which AS quartile does support windowing queries as well as many FROM emp analytic functions. WHERE dept_id = 123;
SQL function OUT/IN OUT parameters Sybase ASE supports only input parameters for SQL functions. If output parameters are used, rewrite with stored procedures
Non-deterministic SQL Functions (functions whose Sybase ASE supports only deterministic SQL result may be independent of the function input functions. DML, DDL, procedure calls, execute- parameters) immediate, certain function calls and utility This cannot be concluded from PL/SQL keywords commands are not allowed in a SQL function. since Oracle supports only the keyword If these occur in an Oracle SQL Function, rewrite DETERMINISTIC to indicate that a function is with ASE stored procedures deterministic. Non-determinism cannot be indicated explicitly, but only from code inspection.
SQL Aggregate Functions No direct equivalent. Rewrite using available ASE features. CREATE FUNCTION f_aggr (p NUMBER) RETURN NUMBER AGGREGATE USING object-type;
BFILE datatype No direct equivalent A BFILE column stores a locator (link) to a binary file outside of the database
Oracle Streams; Oracle Data Guard Use Sybase Replication Server.
Oracle-to-Sybase Migration Cross-Reference 65
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3
Oracle Sybase ASE ("major rewrite")
Oracle RAC for high-availability Use Sybase ASE Cluster Edition
Oracle Flashback No direct equivalent. Some aspects may be covered by using the ASE "auditing" feature, by using ASE "archive databases", and by using the until_time option when loading a transaction log dump. For other cases, old data values can be retained by means of triggers.
Oracle flashback-related pseudocolumns See "Oracle Flashback" above ORA_ROWSCN, VERSION_XID, VERSION_STARTSCN, VERSION_ENDSCN, VERSION_STARTTIME, VERSION_ENDTIME, VERSION_OPERATION
Oracle Snapshot Standby (combination of data No direct equivalent. Similar functionality can be replication and Flashback) achieved with Replication Server.
Oracle SQL Plan Management Some aspects are covered by abstract query plan association ('abstract plan load') as well as by the Stores and maintains query plans to support the query QPTune utility. However, ASE does not support optimizer to make better decisions: every time a query automatic evaluation of newly generated plans versus gets executed, the query optimizer compares the captured past plans. current query plan with the stored query plan and chooses the better plan automatically. (for DBA/tuning purposes, not affecting application query syntax)
AWR (Automatic Workload Repository) Query metrics are captured in ASE's Stores every query with corresponding performance sysquerymetrics with the 'metrics capture' indicators and metrics in a repository, allowing feature, or through the MDA tables. identifying the top poorly performing queries ASE does not support automatic actions based on automatically (for which query plans managed by captured data Oracle SQL Plan Management will be used when the query are being executed again) (for DBA/tuning purposes, not affecting application query syntax)
Oracle Advanced Queuing Similar concept as ASE's Real-Time Messaging Service (RTMS), which allows direct interfacing from SQL with message bus products like Tibco and MQ Series.
Packages for PL/SQL web access No equivalent. Custom implementation in ASE required. OWA_CUSTOM, OWA_CX, OWA_OPT_LOCK, OWA_SEC, OWA_TEXT, OWA_UTIL
Oracle-to-Sybase Migration Cross-Reference 66
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3
Oracle Sybase ASE ("major rewrite")
Oracle Forms Rewrite with Sybase PowerBuilder. See section 9.2.
Oracle-to-Sybase Migration Cross-Reference 67
ORACLE TO SYBASE ASE MIGRATION GUIDE Rev.1.3
CONTACT INFORMATION
For Europe, Middle East, or Africa inquiries: +(31) 34 658 2999
For Asia-Pacific inquiries: +852 2506 8900 (Hong Kong)
For Latin America inquiries: +770 777 3131 (Atlanta, GA)
SYBASE, INC. WORLDWIDE HEADQUARTERS ONE SYBASE DRIVE DUBLIN, CA 94568-7902 USA Tel: 1 800 8 SYBASE www.sybase.com
Copyright © 2012 Sybase, Inc. All rights reserved. Unpublished rights reserved under U.S. copyright laws. Sybase, and the Sybase logo are trademarks of Sybase, Inc. or its subsidiaries. All other trademarks are the property of their respective owners. ® indicates registration in the United States. Specifications are subject to change without notice.
Oracle-to-Sybase Migration Cross-Reference 68