The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Dec. 23, 1986
Filed:
Jan. 22, 1985
Laura M Haas, Palo Alto, CA (US);
Bruce G Lindsay, San Jose, CA (US);
International Business Machines Corporation, Armonk, NY (US);
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. Upon receipt of the messages at the snapshot table site, a single skip sequential pass across the snapshot in BASE TID sequence is performed to apply the incremental changes. This refreshes the snapshot table to the required state.