The SET EXPLAIN statement supports complete-connection level settings. This means that values in the local session environment at the time of connection are propagated to all new or resumed transactions. These can include the following types of transactions:
If you change the SET EXPLAIN setting within a transaction, the new value is propagated back to the local environment and also to all subsequent new or resumed transactions.
SET OPTIMIZATION, UPDATE STATISTICS
For a description of the EXPLAIN and AVOID_EXECUTE optimizer directives, see Explain-Mode Directives.
For discussions of SET EXPLAIN and of analyzing the output of the optimizer, see your IBM Informix Performance Guide.