Semantic conditions for correctness at different isolation levels

Bernstein, Arthur J.; Lewis, Philip; Lu, Shiyong

doi:10.1109/icde.2000.839387

Cited by 26 publications

(16 citation statements)

References 7 publications

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“…In contrast our work does not require knowledge of the integrity constraints and we show serializability which preserves all integrity conditions. Thus, the results of Bernstein et al [2000] are complementary with ours; our result applies in fewer circumstances than theirs, but offers a stronger conclusion when it does apply. Schenkel and Weikum [2000] show how to ensure the serializability of transactions executed against a federation of independent databases some of which provide Snapshot Isolation rather than two-phase locking.…”

Section: Outline Of the Article And Related Worksupporting

confidence: 59%

“…Also new here is guidance on how to alter an application to prevent nonserializable executions, which could otherwise occur. Bernstein et al [2000] provided a theory that can be used to show that certain applications preserve data integrity constraints when executing under weak isolation levels, including Snapshot Isolation. Bernstein et al [2000] uses explicit knowledge of the data integrity conditions required by each transaction, and it concludes that those specific integrity conditions are preserved.…”

Section: Outline Of the Article And Related Workmentioning

confidence: 99%

“…Bernstein et al [2000] provided a theory that can be used to show that certain applications preserve data integrity constraints when executing under weak isolation levels, including Snapshot Isolation. Bernstein et al [2000] uses explicit knowledge of the data integrity conditions required by each transaction, and it concludes that those specific integrity conditions are preserved. In contrast our work does not require knowledge of the integrity constraints and we show serializability which preserves all integrity conditions.…”

Section: Outline Of the Article And Related Workmentioning

confidence: 99%

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Making snapshot isolation serializable

Fekete

Liarokapis²,

O’Neil³

et al. 2005

ACM Trans. Database Syst.

239

252

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Snapshot Isolation (SI) is a multiversion concurrency control algorithm, first described in Berenson et al. [1995]. SI is attractive because it provides an isolation level that avoids many of the common concurrency anomalies, and has been implemented by Oracle and Microsoft SQL Server (with certain minor variations). SI does not guarantee serializability in all cases, but the TPC-C benchmark application [TPC-C], for example, executes under SI without serialization anomalies. All major database system products are delivered with default nonserializable isolation levels, often ones that encounter serialization anomalies more commonly than SI, and we suspect that numerous isolation errors occur each day at many large sites because of this, leading to corrupt data sometimes noted in data warehouse applications. The classical justification for lower isolation levels is that applications can be run under such levels to improve efficiency when they can be shown not to result in serious errors, but little or no guidance has been offered to application programmers and DBAs by vendors as to how to avoid such errors. This article develops a theory that characterizes when nonserializable executions of applications can occur under SI. Near the end of the article, we apply this theory to demonstrate that the TPC-C benchmark application has no serialization anomalies under SI, and then discuss how this demonstration can be generalized to other applications. We also present a discussion on how to modify the program logic of applications that are nonserializable under SI so that serializability will be guaranteed.

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Section: Outline Of the Article And Related Worksupporting

confidence: 59%

Section: Outline Of the Article And Related Workmentioning

confidence: 99%

Section: Outline Of the Article And Related Workmentioning

confidence: 99%

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Making snapshot isolation serializable

Fekete

Liarokapis²,

O’Neil³

et al. 2005

ACM Trans. Database Syst.

239

252

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“…A quite different approach to ensuring correctness when mixing isolation levels is in [3], which uses specific knowledge of the integrity constraints that are required, and the condition proved is that the given constraint is preserved, rather than more general serializability as in this paper.…”

Section: Related Workmentioning

confidence: 99%

Allocating isolation levels to transactions

Fekete

2005

Proceedings of the Twenty-Fourth ACM SIGMOD-SIGACT-SIGART Symposium on Principles of Database Systems

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Serializability is a key property for executions of OLTP systems; without this, integrity constraints on the data can be violated due to concurrent activity. Serializability can be guaranteed regardless of application logic, by using a serializable concurrency control mechanism such as strict twophase locking (S2PL); however the reduction in concurrency from this is often too great, and so a DBMS offers the DBA the opportunity to use different concurrency control mechanisms for some transactions, if it is safe to do so. However, little theory has existed to decide when it is safe! In this paper, we discuss the problem of taking a collection of transactions, and allocating each to run at an appropriate isolation level (and thus use a particular concurrency control mechanism), while still ensuring that every execution will be conflict serializable. When each transaction can use either S2PL, or snapshot isolation, we characterize exactly the acceptable allocations, and provide a simple graph-based algorithm which determines the weakest acceptable allocation.

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“…While a variety of approaches to global synchronization relax serializability in order to increase concurrency (e.g. [12,24,2,1,5,29]), most contributions argue that it is desirable to accept only serializable schedules [3,23,28,35,10,9,27,13]. Our add-on-protocol offers both, it allows for unrestricted concurrency of global integrity checks with local transactions (i.e.…”

Section: Relation To Other Work and Our Focusmentioning

confidence: 99%

Concurrent Checking of Global Cross-Database Integrity Constraints

Böttcher

2003

IFIP Advances in Information and Communication Technology

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Global integrity of data across the boundaries of single database systems is an important requirement in multi-database systems, but cannot be achieved without transaction synchronization across the boundaries of database systems.The problem is to guarantee that global transactions leave these multiple databases in a globally consistent state and to avoid that global integrity checks unnecessarily block other application transactions. We present a solution that offers both, unlimited concurrency between global integrity constraint checks and local transactions, and increased concurrency of global integrity checks and global application transactions, thereby contributing to a higher performance of global integrity checks. We show that the key idea of our approach, i.e., to lock the integrity constraint itself, leads to a correct and efficiently implementable lock protocol for concurrent integrity constraint checks crossing database system boundaries. Since our approach blocks significantly less resources for global integrity checking than the conventional approach, we consider it to be an important contribution to guarantee global cross-database integrity.

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Semantic conditions for correctness at different isolation levels

Cited by 26 publications

References 7 publications

Making snapshot isolation serializable

Making snapshot isolation serializable

Allocating isolation levels to transactions

Concurrent Checking of Global Cross-Database Integrity Constraints

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