> So from Ivan's post, it seems that if my management thread gain
> exclusive access to the database by gaining the semaphore first,
> followed by excuting the "ALTER DATABASE BEGIN BACKUP" SQL before
> start file copy, and executes the "ALTER DATABASE END BACKUP" will
> address the problem of having the backed up copy of the database file
> being corrupted.

You do not need any semaphore. While the database is locked by "ALTER DATABASE
BEGIN BACKUP" the Firebird will not touch the db file, but you do not need
to interrupt your work with that db because all changes are sent to temporary file.

Ivan