Oracle8 Distributed Database Systems Release 8.0 December 1997 Part No. A58247-01 Oracle8 Distributed Database Systems Part No. A58247-01 Release 8.0 Copyright © 1996, 1997, Oracle Corporation. All rights reserved. Primary Author: Jason Durbin Contributing Authors: Steve Bobrowski, Peter Vasterd Contributors: John Bellemore, Anupam Bhide, Roger Bodamer, Jacco Draaijer, Diana Foch-Laurentz, Nina Lewis, Raghu Mani, Basab Maulik, Denise Oertel, Paul Raveling, Kendall Scott, Gordon Smith, Katia Tarkhanov, Sandy Venning, Eric Voss The programs are not intended for use in any nuclear, aviation, mass transit, medical, or other inher- ently dangerous applications. It shall be licensee's responsibility to take all appropriate fail-safe, back up, redundancy and other measures to ensure the safe use of such applications if the Programs are used for such purposes, and Oracle disclaims liability for any damages caused by such use of the Pro- grams. 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Contents How Oracle8 Distributed Database Systems is Organized........................................... Preface-xvi Conventions Used in This Guide ............................................................................... Preface-xviii Your Comments Are Welcome............................................................................................ Preface-xix 1 Distributed Database Concepts Oracle’s Distributed Database Architecture.................................................................................. 1-2 Clients and Servers...................................................................................................................... 1-2 The Network.................................................................................................................................. 1-4 Databases and Database Links ................................................................................................... 1-4 Database Links .............................................................................................................................. 1-5 Schema Object Name Resolution ............................................................................................... 1-6 Connecting Between Oracle Server Versions ........................................................................... 1-7 Distributed Databases and Distributed Processing................................................................. 1-7 Distributed Databases and Database Replication.................................................................... 1-7 Heterogeneous Distributed Databases........................................................................................... 1-8 Heterogeneous Services............................................................................................................... 1-8 Heterogeneous Services Agents ................................................................................................. 1-9 Features .......................................................................................................................................... 1-9 Developing Distributed Database Applications........................................................................ 1-10 Remote and Distributed SQL Statements ............................................................................... 1-10 Remote Procedure Calls (RPCs) ............................................................................................... 1-11 Remote and Distributed Transactions..................................................................................... 1-11 Transparency in a Distributed Database System ................................................................ 1-13 iii Administering an Oracle Distributed Database System........................................................... 1-15 Site Autonomy............................................................................................................................ 1-15 Distributed Database Security .................................................................................................. 1-16 Tools for Administering Oracle Distributed Databases........................................................ 1-17 Enterprise Manager .................................................................................................................... 1-17 Third-Party Administration Tools ........................................................................................... 1-18 SNMP Support ............................................................................................................................ 1-18 National Language Support............................................................................................................ 1-19 2 Distributed Database Administration Global Database Names and Global Object Names.................................................................... 2-2 Types of Database Links.................................................................................................................... 2-3 Private, Public, and Global Database Links.............................................................................. 2-3 Security Options for Database Links ......................................................................................... 2-4 Shared Database Links................................................................................................................. 2-6 Connection Qualifiers ................................................................................................................ 2-13 Database Link Resolution.......................................................................................................... 2-14 Schema Object Name Resolution.............................................................................................. 2-15 Views, Synonyms, Procedures and Global Name Resolution ............................................. 2-17 Dropping a Database Link......................................................................................................... 2-19 Listing Available Database Links............................................................................................. 2-19 Limiting the Number of Active Database Links .................................................................... 2-19 Techniques for Location Transparency ......................................................................................... 2-20 Views and Location Transparency........................................................................................... 2-20 Synonyms and Location Transparency ................................................................................... 2-22 Procedures and Location Transparency.................................................................................. 2-24 Statement Transparency................................................................................................................... 2-25 Restrictions................................................................................................................................... 2-26 Values for Environmentally-Dependent SQL Functions ...................................................... 2-26 Shared SQL for Remote and Distributed Statements ............................................................ 2-26 iv 3 Distributed Transactions Distributed Transaction Management............................................................................................ 3-2 The Prepare and Commit Phases..................................................................................................... 3-2 Prepare Phase...............................................................................................................................