Hello,

the same statement with the same execution plan is running much slower
on different occasions? Co-operative garbage collection in Firebird
Classic and SuperClassic might be the root cause.

Check out this demo how to get some feedback if garbage collection has
been additionally performed for an executed statement:

http://www.iblogmanager.com/download/demos/fbtm/fbtm_30_garbage_collection.htm


--
With regards,
Thomas Steinmaurer
http://www.upscene.com/
Professional Tools and Services for Firebird
FB TraceManager, IB LogManager, Database Health Check, Tuning etc.