> I can't find the oldest active transaction in mon$transactions and sweep
> has no effect. Even Sinatica Monitor and IBExpert doesn't show this number.
> How can I rollback this transaction?

"oldest active transaction" does not mean "oldest of currently running transactions",
but "oldest transaction that was active when some other currently active transaction started".
Is that clear ? :)

So, it is normal that such transaction is already closed when you retrieve its number from e.g. mon$database

Ivan