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Minimizing Logging to Facilitate Recovery of Tablespace

IP.com Disclosure Number: IPCOM000038450D
Original Publication Date: 1987-Jan-01
Included in the Prior Art Database: 2005-Jan-31
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Cowdery, LR: AUTHOR [+3]

Abstract

This invention relates to a method for minimizing logging required to facilitate the recovery of tablespace reorganization. In relational data base management systems such as DB2, recoverability of a tablespace is achieved by making a copy of the tablespace as it exists at a checkpoint, and then logging changes to the tablespace after the checkpoint. When the copy of the tablespace is made, a description of the copied data set and the current location of the log are added to a designated storage, such as the DB2 SYSCOPY table.

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Minimizing Logging to Facilitate Recovery of Tablespace

This invention relates to a method for minimizing logging required to facilitate the recovery of tablespace reorganization. In relational data base management systems such as DB2, recoverability of a tablespace is achieved by making a copy of the tablespace as it exists at a checkpoint, and then logging changes to the tablespace after the checkpoint. When the copy of the tablespace is made, a description of the copied data set and the current location of the log are added to a designated storage, such as the DB2 SYSCOPY table. Reorganization of the tablespace, by which unused space of the tablespace is deleted and redistributed, is performed by reloading individual rows of the tablespace into a sequential data set, called an unload data set, setting the tablespace at empty, and reloading the rows back to the tablespace in the same order as they were unloaded. To ensure recoverability of the reorganization, the reloading activities are logged, thus creating a large volume of log records and significantly increasing processing time. To eliminate the need for logging the reloading activities, an entry is inserted into the designated storage, such as the DB2 SYSCOPY table, describing the unload data set. The location of the log when the reorganization process is completed is stored. If recovery is needed, the reloading process of the reorganization is repeated utilizing the description of the unload data set and...