>I'm running FB 2.5.2 (Classic) and I have few "heavy" statements.
>These are doing about 70k-500k indexed reads (depending on time of day
>etc.). But few times a day I get 600 000 000 indexed reads. Absolutely
>out of proportion. I was running the application locally to see
>whether I can replicate it, but no luck. Only on server (no obvious
>task like backups (nor FB nor anything else) or sweep is running
>during that time). Any hints what could cause Firebird to do this?

Could it be that statistics are not up to date on your production db? So that it uses a different plan?