Subject Firebird WI-2.5.5: Super large Temp File (50+ GB)


we're using Firebird V.2.5.4 and V.2.5.5 on Windows (Superserver architecture). After the first connect to the database, firebird creates a temp file (named like "FB_TABLE_xyz" with no extension in a Windows temp directory). Initially, this file has a few hundret Kilobytes, but it is growing over time. The database file itself may not be too large, but that temp file grows over time (days, weeks) and we saw such files of 50 Gigabytes (!!) and more.

It doesn't grow constantly, but from time to time it suddenly takes a few GB more (and eventually waste all the available HD space after some time).

From what I read about Firebird Temp files, I understand that there are two kind of temp files: Sort files and files that are used to swap out data in Global Temporary Tables (GTT). Sort files would have the word "sort" in its name, so I assume this is a GTT temp file.

Usually the temp file becomes auto-deleted when all users disconnect from firebird (although we saw situations where the Firebird server needed to be restarted to kill the file). But usually there are always some active database connection (24x7 applcation).

In fact we're using some GTTs and we analyzed their usage of course. We do not find any reason that would nearly explain this enourmous temp file size (many time the size of the entire main database), however. Also, transactions are not very-long active.

My questions:
1) Is there any known bug und suspicion about GTTs-temp files?
2) Is there any tool, audit, logging mechanism that would allow me to analyze the origin of the temp data or other traces that could help to understand the problem or to identify a bug?