METHOD AND APPARATUS FOR POINTER RELOCATION OPTIMIZATION FOR VIRTUAL MEMORY MAPPING AND TRANSACTION MANAGEMENT IN A DATABASE SYSTEM

There is provided an apparatus and a method for virtual memory mapping and transaction management for an object-oriented data base system having at least one permanent storage means for storing data and at least one data base, at least one cache memory for locally storing data addressed by physical addresses, and a processing unit including means for requesting data utilizing virtual addresses to access data in the cache memory, means for mapping virtual addresses to physical addresses and means for retaining the cached data after the conclusion of a transaction. The apparatus and method further provide that data retained in the cache across transactions will often not need further translation, referred to as forward relocation. The ability to make cached data usable across a sequence of transactions often without requiring further translation, while also providing that the total working set size of this data may be much larger than what can fit into a client computer's address space at any one time is referred to as relocation optimization, and is the primary advantage of this method. The method makes use of a single queue containing elements representing managed entities (pages, address space bindings) which orders the entities roughly by recency of use, and recycles address space of the least-recently used bindings in a way that preserves the validity of bindings necessary for the proper function of the client application with minimal overhead.