Quickbooks users have noticed that besides the company data file with extension .qbw, there exists a few other files that mysteriously come and go and change size.
One of the files is filename.qbw.tlg Frequently this file's size outstrips the actual data in size, I have seen up to a factor of 10 pretty often. Some users complain that this file slows the system. I have not personally verified this, but it is quite possible. Deleting this file seems to have no impact, but who wants to do that?
After following a number of leads I have finally discovered it's use:
This file simply tracks changes since the last full backup was made. Making a fresh backup resets this file to a couple of bytes. It seems that if you lose your data file today, and your last backup was a month ago, restoring from the backup happens normally and quickbooks then apples the changes recorded in the tlg file that were made since that backup.
Sounds nifty but for obvious reasons I have not tested it, but will do so soon. So in short, if your quickbooks seems a bit slower than usual, shrink the tlg file by doing a full backup from within quickbooks.