METHOD AND SYSTEM FOR SUPPORTING CONCURRENT USE DURING SEQUENTIAL BATCH APPLICATIONS UTILIZING PERSISTENT CURSORS

摘要

A method is disclosed for supporting sequential batch applications within a data processing system which permits the continued enumeration of a sequence of objects across a transaction commit, roll-back or system failure. A query is defined which specified a set of objects and a named cursor is associated with the query, each cursor including at least one scan which may be utilized to evaluate and enumerate the query. Selected cursors may be designated as persistent cursors and stored, along with the state of any associated scan(s) and a query evaluation state in a persistent cursor table (PCT) in response to a transaction commit. Thereafter, the evaluation an enumeration of the query may be reestablished at the point of a persistent cursor by utilizing the information stored within the persistent cursor table (PCT). In the event of a subsequent roll-back of a transaction prior to the next commit point the query may be reestablished at the previous commit point utilizing the information stored within the persistent cursor table (PCT). A cursor may also be designated as a restartable cursor and stored, along with all information within the persistent cursor table (PCT), in non-volatile memory. Thereafter, in the event of a system failure the evaluation and enumeration of the query may be reestablished at the point of a restartable cursor by utilizing the information stored within non-volatile memory.