Stefan wrote:
<<
Database header page information:
...
Oldest transaction 288095
Oldest active 288096
Oldest snapshot 76544
Next transaction 501810
...

>>

This _could_ indicate that garbage is accumulating in the database,
and no tuning of Firebird will fix this. The problem would then be
the programs which probably don't handle transactions properly.
Using "CommitRetaining" (with hardly any "Commit") is a prime suspect.

--
Aage J.