Constrained (Slow Path) DELETE Processing
The processing time for a constrained delete (DELETE...WHERE) can increase when:
The DELETE does not meet the conditions for a fastpath delete processing. See “Unconstrained Fastpath Delete Processing” on page 324.
The FALLBACK option is specified for the table, because the rows in the secondary
copy of the table must also be deleted.
Secondary indexes are defined for the table, because the secondary index subtable
also must be updated to account for the rows deleted.
Processing time for a constrained delete can be shortened by specifying a primary
index value, a USI value, or a highly selective NUSI value as the conditional expression
of the WHERE clause.