Siebel Database Upgrade Guide for DB2 UDB for z/OS > Planning A Siebel Database Upgrade >
About Database Clustered Indexes
Upgrades: Release 6.2.1 only.
Environments: All environments.
If you created clustered indexes on base tables, and the upgrade introduces a different clustered index on the same table, the upgrade process re-creates custom indexes as nonclustered and creates the Siebel index as clustered.
For IBM DB2, indexes that reside on tables with append mode enabled are re-created as nonclustered indexes during the upgrade. (Tables created with append mode enabled do not support clustered indexes.)