Speculation based protocols for improving the Performance of read only transactions

Abstract

In the emerging web databases and e-commerce scenario, information systems have to meet intensive information requirements from a large number of users. These information systems receive both update transactions (UTs) and read-only transactions (ROTs). A UT contains both read and write operations and an ROT newlinecontains only read operations. Designing efficient protocols to process ROTs is a research issue. There are newlinethree aspects for designing a concurrency control protocol for processing ROTs: correctness, data currency newlineand performance. The protocol should process transactions by satisfying serializability criteria. Also, the newlineprotocol should process transactions without any data currency issues. Note that data currency is another newlineimportant aspect of the protocol. A protocol should process the ROTs without missing the effect of any newlinepreceding UTs. Finally, the protocol should give high performance. newlineIf both the UTs and ROTs are processed with the popular two-phase locking (2PL) protocol, the performance degrades with the data contention as the UTs have to wait for ROTs and vice versa in case of a newlineconflict. On the other hand, it can be noted that, the 2PL processes ROTs without any correctness and data newlinecurrency issues. So, efforts are being made to propose improved protocols by exploiting the special property newlineof ROT that it does not modify the data and by compromising on correctness and data currency. There are newlineefforts to improve the performance by processing ROTs with multi-version based approaches, at lower isolation levels, and by compromising correctness. One of the popular protocols is snapshot isolation (SI)-based newlineprotocol, in which an ROT reads the snapshot of the database ignoring modifications done by preceding UTs. newlineIn SI-based protocols, even though performance is improved, both correctness and data currency aspects are newlinecompromised. newlineThe 2PL protocol suffers from the performance problems and SI-based protocol suffers from both correctness and data currency problems. So, the research challenge is to develop