Expression-based indexes and manual statistics updates

You can manually update statistics for expression-based key columns by issuing the UPDATE statement against the SYSSTAT.TABLES, SYSSTAT.COLUMNS, and SYSSTAT.COLDIST catalog views.

When you issue the UPDATE statement against the SYSSTAT views, specify the statistical view's name and the name of the column as it appears in the statistical view.

Automatic statistics collection does not occur if you manually update a table's statistics by issuing an UPDATE statement against SYSSTAT catalog views. This condition includes manual updates of expression-based key column statistics for any expression-based indexes that the table has, even though those statistics are in a separate statistical view. Similarly, if you manually update any statistics in the statistical view that is associated with a table with an expression-based index, the underlying table is excluded from automatic statistics collection. To get automatic statistics collection to consider the table, issue the RUNSTATS command against the table rather than the statistical view.