Locking in OODBMS client supporting nested transactions

Abstract

Nested transactions facilitate the control of complex persistent applications by enabling both fine-tuning of the scope of rollback and safe intra-transaction parallelism. We are concerned with supporting concurrent nested transactions on client workstations of an OODBMS. Use of the traditional design and implementation of a lock manager results in a high CPU overhead: in-cache traversals of the 007 benchmark perform, at best, 4.5 times slower than the same traversal achieved in virtual memory by a nonpersistent programming language. We propose a new design and implementation of a lock manager which cuts that factor down to 1.8. This lock manager supports nested transactions with both sibling and parent/child parallelisms, and provides object locking at a cost comparable to page locking. Object locking is therefore a better alternative due to its higher functionality.<>