Cursor pre-fetching

Abstract

Techniques determine a quantity of rows to fetch based on memory available on a client computer and the fetch state of cursors. The techniques are used to determine a quantity of rows for “pre-fetching”. Under pre-fetching, rows in addition to those requested by an application are fetched from a database instance and stored in a “pre-fetch buffer”. The pre-fetch quantities are based on an amount of memory that is deemed available for pre-fetch buffers on a client computer and the number of cursors in the fetch state for a session at a given moment. Pre-fetching is used to hasten session migration. By fetching a quantity of rows that is larger than would be fetched if only the application-specified quantity were fetched, the fetch phase of a cursor is completed sooner. An earlier completion of the fetch phase of a session's cursors allows migration of the session to be completed sooner.

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