Henry F. Korth, Greg SpeegleAuthors Info & ClaimsToday's main-memory databases can support very high transaction rate for OLTP applications. However, when a large number of concurrent transactions contend on the same data records, the system performance can deteriorate significantly. This is ...
The concurrency of transactions executing on atomic data types can be enhanced through the use of semantic information about operations defined on these types. Hitherto, commutativity of operations has been exploited to provide enchanced concurrency ...
A read-only transaction (ROT) or a query is a transaction that only reads data items, without modifying them. When we use a protocol that takes care of ROTs distinctively from update transactions, the number of conflicts between ROTs and update ...
Fred J. Maryanski
Long-duration transactions require criteria beyond serializability to ensure the correctness of an execution. Korth and Speegle's NT/PV model utilizes nested transactions, explicit predicates, and multiple versions to represent the semantics of long-duration transactions. The model defines correctness by imposing restrictions on the executions of transactions. The VPC protocol for correct executions uses partial ordering to create a version set that a transaction may access. Under VPC, transactions satisfy user-supplied correctness predicates and do not commit until all subtransactions terminate. The authors provide a proof of correctness and illustrate the operation of the protocol via an extensive hypothetical example. This work builds on prior research in the area in a coherent manner and appears to present a firm foundation for integration into a complete DBMS.
Özgür Ulusoy
A transaction model is presented that provides a basis for developing new correctness criteria that allow more concurrency for long-duration transactions than the traditional serializability criterion. The proposed transaction model, called the NT/PV model, incorporates three semantic enhancements to the standard model: nested transactions, explicit predicates, and multiple versions. These enhancements enable the model to capture the semantics of long-duration transaction systems. Following a formal presentation of the NT/PV model, the authors show that the features found in multilevel transaction frameworks and predicate-based systems are combined in this model. A concurrency control protocol that allows only NT/PV-correct executions is provided and proven to be correct. The paper also provides a detailed example from the cooperative software design field that fully exploits the NT/PV model. The paper is a good piece of theoretical work. It is well organized and quite readable for researchers familiar with the theory of concurrency control. The list of citations is also helpful. I recommend this paper to anyone interested in transaction processing in database systems.
Become a reviewer for Computing Reviews.
Association for Computing Machinery
New York, NY, United States
Check if you have access through your login credentials or your institution to get full access on this article.
Sign in