SQL Operations That Do Not Use PDQ

The database server does not process the following types of queries in parallel:

• Queries started with an isolation level of Cursor Stability

  Subsequent changes to the isolation level do not affect the parallelism of queries already prepared. This situation results from the inherent nature of parallel scans, which scan several rows simultaneously.

• Queries that use a cursor declared as FOR UPDATE
• An UPDATE statement that has an update trigger that updates in the For Each Row section of the trigger definition
• Data definition language (DDL) statements

  For a complete list, see the IBM Informix: Guide to SQL Syntax.