Improving REORG performance after adding a column

After you add a column to a table space, you can take certain steps to improve performance.

About this task

After a column is added to a table space, the next REORG utility job of that table space creates default values for the new column, as follows:

  • During its UNLOAD phase, the REORG job creates default values by converting all fields in each row to the external DB2® format.
  • During the RELOAD phase, the REORG job then converts the default values to the internal DB2 format.

This REORG processing, referred to as a compression cycle, occurs on each subsequent run of the REORG utility on this table space. You can improve performance by avoiding the compression cycle each time that the REORG job runs on the table space.

Procedure

To improve performance after adding a column to a table space:

  1. Run the REORG utility on the table space.
  2. Run the COPY utility to make a full image copy of the table space.
  3. Run MODIFY RECOVERY with the DELETE or RETAIN option to delete all previous image copies. MODIFY RECOVERY changes the status of the column that is added after using the ALTER statement only if SYSCOPY rows need to be deleted.