(Originally posted 2006-03-30.)
Long ago the DB2 REORG utility traded memory for speed with SORTKEYS and SORTDATA. The latter caused the object being REORGed to be unloaded and externally sorted (eg using DFSORT). (SORTKEYS was similar but for the keys to REORG the indexes.)
This is fine if you have the memory to drive either large
in-memory sorts or multiple parallel sorts. But sometimes you don’t.
APAR PK18059 for V8 introduces SORTDATA YES/NO to allow you to specify whether an individual REORG will use SORTDATA or not.