Reorganization of Tables (DB2 UDB for UNIX and Windows) 

Use

You can use the DBA Planning Calendar to schedule a reorganization of a set of tables. The actions for reorganizing tables are listed on the Action Pad.

Features

There are different ways to reorganize your tables:

·        REORG and RUNSTATS of Flagged Tables 

Whenever a RUNSTATS and REORGCHK have been executed, the REORGCHK recommendations are collected in a special table. If you plan this action, you get a list of the recommended tables and can select all or a subset of them.

This action cannot be scheduled periodically.

·        REORG and RUNSTATS for Single Table

This action schedules a REORGfor a table specified by the user.  

·        REORG of Tables in Tablespace(s)     

This action schedules a REORGaction that reorganizes all tables for a list of tablespaces which can be defined as parameters. This action is useful if the high-water marks of a tablespace need to be reduced.

·        Automatic REORG

A basic condition before doing any REORG is that the table statistics are up-to-date and have been created using the RUNSTATS programs.

Furthermore, this action also needs the Check Tables for Statistics Update action, which collects I/O numbers of tables.

This action schedules a REORGaction which looks for REORG candidates according to rules, which may be set by the following action parameters:

Parameter	Description
Overflow Threshold	Percentage of overflows on this table in relation to the size of the table
Maximum Size of Table	Maximum size of the table as known from the last RUNSTATS/ REORGCHK
Maximum Runtime	Maximum runtime for the action Be aware that the value displayed is not exact. It is only checked after the reorganization of each table. If the value reaches the limit during reorganization, the action will not be interrupted.

For all REORG actions, a temporary tablespace can be specified optionally. If no temporary tablespace is used for REORG, REORG is done within the tablespace where the table or index resides. There must be enough free space in this tablespace (approximately the size of the table or index). If this tablespace has already a high I/O load, it might be better for the performance of the database to use a temporary tablespace.