Speculation based nested locking protocol to increase the concurrency of nested transactions
P. Krishna Reddy, Masaru Kitsuregawa · 2002
The authors propose an improved concurrency control protocol based on speculation for nested transactions and explain how it increases both intraand inter-transaction concurrency as compared to J.E.B. Moss's (1985) nested locking protocol. In the proposed speculative nested locking (SNL) protocol, whenever a sub-transaction finishes work with a data object (produces after-image), it's parent inherits the lock. The waiting sub-transaction carries out speculative executions by accessing both before- and after-images of preceding sub-transaction and selects appropriate execution after the termination of the preceding subtransaction. In this way, SNL allows multiple executions to be carried out for a transaction by trading extra processing and main memory resources to increase concurrency.