Using Tickets to Enforce the Serializability of Multidatabase Transactions
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An Efficient Concurrency Control Technique for Mobile Database Environment by Md
View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Global Journal of Computer Science and Technology (GJCST) Global Journal of Computer Science and Technology Software & Data Engineering Volume 13 Issue 2 Version 1.0 Year 2013 Type: Double Blind Peer Reviewed International Research Journal Publisher: Global Journals Inc. (USA) Online ISSN: 0975-4172 & Print ISSN: 0975-4350 An Efficient Concurrency Control Technique for Mobile Database Environment By Md. Anisur Rahman Dhaka University of Engineering & Technology Gazipur, Bangladesh Abstract - Day by day, wireless networking technology and mobile computing devices are becoming more popular for their mobility as well as great functionality. Now it is an extremely growing demand to process mobile transactions in mobile databases that allow mobile users to access and operate data anytime and anywhere, irrespective of their physical positions. Information is shared among multiple clients and can be modified by each client independently. However, for the assurance of timely access and correct results in concurrent mobile transactions, concurrency control techniques (CCT) happen to be very difficult. Due to the properties of Mobile databases e.g. inadequate bandwidth, small processing capability, unreliable communication, mobility etc. existing mobile database CCTs cannot employ effectively. With the client-server model, applying common classic pessimistic techniques of concurrency control (like 2PL) in mobile database leads to long duration Blocking and increasing waiting time of transactions. Because of high rate of aborting transactions, optimistic techniques aren`t appropriate in mobile database as well. This paper discusses the issues that need to be addressed when designing a CCT technique for Mobile databases, analyses the existing scheme of CCT and justify their performance limitations. -
A View-Based Approach to Relaxing Global Serializability in Multidatabase Systems
Purdue University Purdue e-Pubs Department of Computer Science Technical Reports Department of Computer Science 1993 A View-Based Approach to Relaxing Global Serializability in Multidatabase Systems Aidong Zhang Evaggelia Pitoura Bharat K. Bhargava Purdue University, [email protected] Report Number: 93-082 Zhang, Aidong; Pitoura, Evaggelia; and Bhargava, Bharat K., "A View-Based Approach to Relaxing Global Serializability in Multidatabase Systems" (1993). Department of Computer Science Technical Reports. Paper 1095. https://docs.lib.purdue.edu/cstech/1095 This document has been made available through Purdue e-Pubs, a service of the Purdue University Libraries. Please contact [email protected] for additional information. A VIEW-BASED APPROACH TO RELAXING GLOBAL SERIALIZABILITY IN MULTIDATABASE SYSTEMS Aldong Zhang Evaggelia PitOUI'3 Bharat Bh:Jrgava CSD TR-9J.082 December 1993 (Revised March 1994) A View-Based Approach to Relaxing Global Serializability in Multidatabase Systems Aidong Zhang, Evaggelia Pitoura, and Bharat K Bhargava Department of Computer Science Purdue University West Lafayette, IN 47907 USA Abstract In this paper, we propose a new approach to ensuring the correctness of non serializable executions. The approach is based on relating transaction views of the database to the integrity constraints of the system. Drawing upon this approach, we de velop a new correctness criterion for multidatabase concurrency control. This criterion, caUed view-based two-level serializability, relaxes global serializabitity in multidatabase systems while respecting the autonomy of local database systems. No additional re strictions other than serializallility are imposed on local database systems. 1 Introduction A Illultidataba.-<;e system (MDBS) is a higher-level confederation of a nWllber of pre-existing autonomolls and possibly heterogeneous database systems. -
Concurrency Control Basics
Outline l Introduction/problems, l definitions Introduction/ (transaction, history, conflict, equivalence, Problems serializability, ...), Definitions l locking. Chapter 2: Locking Concurrency Control Basics Klemens Böhm Distributed Data Management: Concurrency Control Basics – 1 Klemens Böhm Distributed Data Management: Concurrency Control Basics – 2 Atomicity, Isolation Synchronisation, Distributed (1) l Transactional guarantees – l Essential feature of databases: in particular, atomicity and isolation. Many users can access the same data concurrently – be it read, be it write. Introduction/ l Atomicity Introduction/ Problems Problems u Example, „bank scenario“: l Consistency must be guaranteed – Definitions Definitions task of synchronization component. Locking Number Person Balance Locking Klemens 5000 l Multi-user mode shall be hidden from users as far as possible: concurrent processing Gunter 200 of requests shall be transparent, u Money transfer – two elementary operations. ‚illusion‘ of being the only user. – debit(Klemens, 500), – credit(Gunter, 500). l Isolation – can be explained with this example, too. l Transactions. Klemens Böhm Distributed Data Management: Concurrency Control Basics – 3 Klemens Böhm Distributed Data Management: Concurrency Control Basics – 4 Synchronisation, Distributed (2) Synchronization in General l Serial execution of application programs Uncontrolled non-serial execution u achieves that illusion leads to other problems, notably inconsistency: l Introduction/ without any synchronization effort, Introduction/ -
Effective Technique for Optimizing Timestamp Ordering in Read- Write/Write-Write Operations
International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 06 Issue: 09 | Sep 2019 www.irjet.net p-ISSN: 2395-0072 Effective Technique for Optimizing Timestamp Ordering in Read- Write/Write-Write Operations Obi, Uchenna M1, Nwokorie, Euphemia C2, Enwerem, Udochukwu C3, Iwuchukwu, Vitalis C4 1Lecturer, Department of Computer Science, Federal University of Technology, Owerri, Nigeria 2Senior Lecturer, Department of Computer Science, Federal University of Technology, Owerri, Nigeria 3Lecturer, Department of Computer Science, Federal University of Technology, Owerri, Nigeria 4Lecturer, Department of Computer Science, Federal University of Technology, Owerri, Nigeria ---------------------------------------------------------------------***---------------------------------------------------------------------- Abstract - In recent times, the use of big data has been the measures, these are: read-write (RW) synchronization and trending technology, most enterprises tend to adopt large write-write (WW) synchronization. databases, but the inherent problem is how to ensure serializability in concurrent transactions that may want to Concurrency control techniques are employed for managing access the data in the database so as to maintain its data concurrent access of transactions on a particular data item integrity and not to compromise it. The aim of this research is by ensuring serializable executions or to avoid interference to develop an efficient Timestamp Ordering algorithm and among transactions and thereby helps in avoiding errors and model in conflicting operations in read-write/write-write data maintain consistency of the database. Various concurrency synchronization. In read-write synchronization, one of the control techniques have been developed by different operations to perform is read while the other is write researchers and these techniques are distinct and unique in operation. -
Cache Serializability: Reducing Inconsistency in Edge Transactions
Cache Serializability: Reducing Inconsistency in Edge Transactions Ittay Eyal Ken Birman Robbert van Renesse Cornell University tributed databases. Until recently, technical chal- Abstract—Read-only caches are widely used in cloud lenges have forced such large-system operators infrastructures to reduce access latency and load on to forgo transactional consistency, providing per- backend databases. Operators view coherent caches as object consistency instead, often with some form of impractical at genuinely large scale and many client- facing caches are updated in an asynchronous manner eventual consistency. In contrast, backend systems with best-effort pipelines. Existing solutions that support often support transactions with guarantees such as cache consistency are inapplicable to this scenario since snapshot isolation and even full transactional atom- they require a round trip to the database on every cache icity [9], [4], [11], [10]. transaction. Our work begins with the observation that it can Existing incoherent cache technologies are oblivious to be difficult for client-tier applications to leverage transactional data access, even if the backend database supports transactions. We propose T-Cache, a novel the transactions that the databases provide: trans- caching policy for read-only transactions in which incon- actional reads satisfied primarily from edge caches sistency is tolerable (won’t cause safety violations) but cannot guarantee coherency. Yet, by running from undesirable (has a cost). T-Cache improves cache consis- cache, client-tier transactions shield the backend tency despite asynchronous and unreliable communication database from excessive load, and because caches between the cache and the database. We define cache- are typically placed close to the clients, response serializability, a variant of serializability that is suitable latency can be improved. -
On Ordering Transaction Commit
On Ordering Transaction Commit Mohamed M. Saad Roberto Palmieri Binoy Ravindran Virginia Tech msaad, robertop, binoy @vt.edu { } Complete Commit Execute Abstract Ordering In this poster paper, we briefly introduce an effective solution to Time address the problem of committing transactions enforcing a pre- α defined order. To do that, we overview the design of two algorithms γ that deploy a cooperative transaction execution that circumvents the δ transaction isolation constraint in favor of propagating written val- β ues among conflicting transactions. A preliminary implementation shows that even in the presence of data conflicts, the proposed al- gorithms outperform other competitors, significantly. Categories and Subject Descriptors D.1.3 [Software]: Concur- rent Programming; H.2.4 [Systems]: Transaction processing (a) BS 4 Thr. (b) BS 8 Thr. (c) FH Commit (d) FH Complete Keywords Transactional Memory, Commitment Ordering Figure 1: ACO using Blocking/Stall (BS) and Freeze/Hold (FH) 1. Introduction semantics (of the parallel code) that is equivalent to the original Transactional Memory (TM) [5] is an easy abstraction to program (sequential) code. Regarding the latter, SMR-based transactional concurrent applications. Its integration into main-stream compilers systems order transactions (totally or partially) before their execu- and programming languages such as GCC and C++ gives TM, tion to guarantee that a state always evolves on several computing respectively, accessibility and concreteness. nodes, consistently. To do that, usually a consensus protocol is em- In this poster paper we provide the design of two TM implemen- ployed (e.g., Paxos [6]), which establishes a common order among tations that commit transactions enforcing an order defined prior to transactions. -
Serializability, Not Serial: Concurrency Control and Availability in Multi-Datacenter Datastores
Serializability, not Serial: Concurrency Control and Availability in Multi-Datacenter Datastores Stacy Patterson1 Aaron J. Elmore2 Faisal Nawab2 Divyakant Agrawal2 Amr El Abbadi2 1Department of Electrical Engineering 2Department of Computer Science Technion - Israel Institute of Technology University of California, Santa Barbara Haifa, 32000, Israel Santa Barbara, CA 93106 [email protected] faelmore,nawab,agrawal,[email protected] ABSTRACT create applications within the eventual consistency model We present a framework for concurrency control and avail- [21]. Many cloud providers then introduced support for ability in multi-datacenter datastores. While we consider atomic access to individual data items, in essence, provid- Google's Megastore as our motivating example, we define ing strong consistency guarantees. This consistency level general abstractions for key components, making our solu- has become a standard feature that is offered in most cloud tion extensible to any system that satisfies the abstraction datastore implementations, including BigTable, SimpleDB, properties. We first develop and analyze a transaction man- and Apache HBase [17]. Strong consistency of single data agement and replication protocol based on a straightforward items is sufficient for many applications. However, if several implementation of the Paxos algorithm. Our investigation data items must be updated atomically, the burden to imple- reveals that this protocol acts as a concurrency prevention ment this atomic action in a scalable, fault tolerant manner mechanism rather than a concurrency control mechanism. lies with the software developer. Several recent works have We then propose an enhanced protocol called Paxos with addressed the problem of implementing ACID transactions Combination and Promotion (Paxos-CP) that provides true in cloud datastores [3, 11, 12], and, while full transaction transaction concurrency while requiring the same per in- support remains a scalability challenge, these works demon- stance message complexity as the basic Paxos protocol. -
A Study of the Availability and Serializability in a Distributed Database System
A STUDY OF THE AVAILABILITY AND SERIALIZABILITY IN A DISTRIBUTED DATABASE SYSTEM David Wai-Lok Cheung B.Sc., Chinese University of Hong Kong, 1971 M.Sc., Simon Fraser University, 1985 A THESIS SUBMI'ITED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHLLOSOPHY , in the School of Computing Science 0 David Wai-Lok Cheung 1988 SIMON FRASER UNIVERSITY January 1988 All rights reserved. This thesis may not be reproduced in whole or in part, by photocopy or other means, without permission of the author. 1 APPROVAL Name: David Wai-Lok Cheung Degree: Doctor of Philosophy Title of Thesis: A Study of the Availability and Serializability in a Distributed Database System Examining Committee: Chairperson: Dr. Binay Bhattacharya Senior Supervisor: Dr. TikoJameda WJ ru p v Dr. Arthur Lee Liestman Dr. Wo-Shun Luk Dr. Jia-Wei Han External Examiner: Toshihide Ibaraki Department of Applied Mathematics and Physics Kyoto University, Japan Bate Approved: January 15, 1988 PARTIAL COPYRIGHT LICENSE I hereby grant to Simon Fraser University the right to lend my thesis, project or extended essay (the title of which is shown below) to users of the Simon Fraser University Library, and to make partial or single copies only for such users or in response to a request from the library of any other university, or other educational institution, on its own behalf or for one of its users. I further agree that permission for multiple copying of this work for scholarly purposes may be granted by me or the Dean of Graduate Studies. It is understood that copying or publication of this work for financial gain shall not be allowed without my written permission, T it l e of Thes i s/Project/Extended Essay Author: (signature) ( name (date) ABSTRACT Replication of data objects enhances the reliability and availability of a distributed database system. -
A Theory of Global Concurrency Control in Multidatabase Systems
VLDB Journal,2, 331-360 (1993), Michael Carey and Patrick Valduriez, Editors 331 t~)VLDB A Theory of Global Concurrency Control in Multidatabase Systems Aidong Zhang and Ahmed K. Elmagarmid Received December 1, 1992; revised version received February 1, 1992; accepted March 15, 1993. Abstract. This article presents a theoretical basis for global concurrency control to maintain global serializability in multidatabase systems. Three correctness criteria are formulated that utilize the intrinsic characteristics of global transactions to de- termine the serialization order of global subtransactions at each local site. In par- ticular, two new types of serializability, chain-conflicting serializability and shar- ing serializability, are proposed and hybrid serializability, which combines these two basic criteria, is discussed. These criteria offer the advantage of imposing no restrictions on local sites other than local serializability while retaining global se- rializability. The graph testing techniques of the three criteria are provided as guidance for global transaction scheduling. In addition, an optimal property of global transactions for determinating the serialization order of global subtransac- tions at local sites is formulated. This property defines the upper limit on global serializability in multidatabase systems. Key Words. Chain-conflicting serializability, sharing serializability, hybrid serial- izability, optimality. 1. Introduction Centralized databases were predominant during the 1970s, a period which saw the development of diverse database systems based on relational, hierarchical, and network models. The advent of applications involving increased cooperation between systems necessitated the development of methods for integrating these pre-existing database systems. The design of such global database systems must allow unified access to these diverse database systems without subjecting them to conversion or major modifications. -
Chapter 14: Concurrency Control
ChapterChapter 1515 :: ConcurrencyConcurrency ControlControl What is concurrency? • Multiple 'pieces of code' accessing the same data at the same time • Key issue in multi-processor systems (i.e. most computers today) • Key issue for parallel databases • Main question: how do we ensure data stay consistent without sacrificing (too much) performance? Lock-BasedLock-Based ProtocolsProtocols • A lock is a mechanism to control concurrent access to a data item • Data items can be locked in two modes: 1. exclusive (X) mode. Data item can be both read as well as written. X-lock is requested using lock-X instruction. 2. shared (S) mode. Data item can only be read. S-lock is requested using lock-S instruction. • Lock requests are made to concurrency-control manager. Transaction can proceed only after request is granted. Lock-BasedLock-Based ProtocolsProtocols (Cont.)(Cont.) • Lock-compatibility matrix • A transaction may be granted a lock on an item if the requested lock is compatible with locks already held on the item by other transactions. • Any number of transactions can hold shared locks on an item, – but if any transaction holds an exclusive on the item no other transaction may hold any lock on the item. • If a lock cannot be granted, the requesting transaction is made to wait till all incompatible locks held by other transactions have been released. The lock is then granted. Lock-BasedLock-Based ProtocolsProtocols (Cont.)(Cont.) • Example of a transaction performing locking: T2: lock-S(A); read (A); unlock(A); lock-S(B); read (B); unlock(B); display(A+B) • Locking as above is not sufficient to guarantee serializability — if A and B get updated in-between the read of A and B, the displayed sum would be wrong. -
Models of Transactions Structuring Applications Flat Transaction Flat
Structuring Applications • Many applications involve long transactions Models of Transactions that make many database accesses • To deal with such complex applications many transaction processing systems Chapter 19 provide mechanisms for imposing some structure on transactions 2 Flat Transaction Flat Transaction • Consists of: begin transaction – Computation on local variables • Abort causes the begin transaction • not seen by DBMS; hence will be ignored in most future discussion execution of a program ¡£ ¤¦©¨ – Access to DBMS using call or ¢¡£ ¥¤§¦©¨ that restores the statement level interface variables updated by the ¡£ ¤¦©¨ • This is transaction schedule; commit ….. applies to these operations ¢¡£ ¤§¦©¨ ….. transaction to the state • No internal structure they had when the if condition then abort • Accesses a single DBMS transaction first accessed commit commit • Adequate for simple applications them. 3 4 Some Limitations of Flat Transactions • Only total rollback (abort) is possible – Partial rollback not possible Providing Structure Within a • All work lost in case of crash Single Transaction • Limited to accessing a single DBMS • Entire transaction takes place at a single point in time 5 6 1 Savepoints begin transaction S1; Savepoints Call to DBMS sp1 := create_savepoint(); S2; sp2 := create_savepoint(); • Problem: Transaction detects condition that S3; requires rollback of recent database changes if (condition) {rollback (sp1); S5}; S4; that it has made commit • Solution 1: Transaction reverses changes • Rollback to spi causes -
CS848 - Cloud Data Management
Cloud Transactions Failures Partitioning Replication CAP Views CS848 - Cloud Data Management Introduction and Background Ken Salem David R. Cheriton School of Computer Science University of Waterloo Winter 2010 • Adjectives associated with clouds • scalable • highly-available • pay-as-you-go • on demand • Not much point in trying to pin down what is cloud and what is not. Cloud Transactions Failures Partitioning Replication CAP Views What is cloud computing? • It seems that everybody who is offering an internet service or using a cluster wants to label themselves “cloud” • Not much point in trying to pin down what is cloud and what is not. Cloud Transactions Failures Partitioning Replication CAP Views What is cloud computing? • It seems that everybody who is offering an internet service or using a cluster wants to label themselves “cloud” • Adjectives associated with clouds • scalable • highly-available • pay-as-you-go • on demand Cloud Transactions Failures Partitioning Replication CAP Views What is cloud computing? • It seems that everybody who is offering an internet service or using a cluster wants to label themselves “cloud” • Adjectives associated with clouds • scalable • highly-available • pay-as-you-go • on demand • Not much point in trying to pin down what is cloud and what is not. Cloud Transactions Failures Partitioning Replication CAP Views Services Spectrum less flexible more flexible more constrained less constrained less effort more effort Cloud Transactions Failures Partitioning Replication CAP Views Services Spectrum less