Abstract: 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 and 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).

Abstract: A method for refreshing a relational data base snapshot manifest in the form of remote read-only copies of selected portions of a base table. The method takes advantage of the fact that each tuple of the base table has a unique identifier TID associated therewith from the time the record is inserted until it is deleted. The TID references the physical location of the tuple within its relation. Two system-maintained fields are added to the base table. These are PREVTID and update ID. One system-maintained column is required in the snapshot table, i.e. BASE TID. Lastly, a column in the catalog of the snapshot is also maintained, i.e. SNAPHIGH.When the refresh of the snapshot table is required, a single scan of the base relation, in ascending TID sequence, is performed on the base table. The scan produces a series of messages which contain the incremental changes required to update the snapshot table to the current state of the base relation.