The QuickBooks transaction log file is a log of all changes about to be made to the company file (.qbw) before they are actually recorded in the company file. It is stored in the same folder as the company file itself. It’s automatically created by QuickBooks.
The filename of the transaction log file is in the form:
[company file name].qbw.TLG
QuickBooks uses data written to the transaction log file to transparently complete the recording of transactions that were not completely recorded in the company file itself because a connection to the company file was lost. The transaction log file can also be used in conjunction with a QuickBooks backup file (.qbb) to recover from a damaged company file.
The transaction log file is reset when:
- you sucessfully complete a manual (not a scheduled or online) backup in QuickBooks
- you restore a portable company file (.qbm)
- the company file does not match the transaction log file
The company file may not match the transaction log file if you restore a backup of the company file using the same filename in the same folder or if you make a copy of a company file, take the copy to another computer and make changes, and put the changed copy back in the original location. For example, if you want to make a copy of the company file and work on it on another computer, you need to copy both the company file itself and the corresponding transaction log file in order to preserve the data recovery benefits that the transaction log file offers.
Because the transaction log file is only reset under specific circumstances, it may grow in size and become larger than the QuickBooks company file itself. Large transaction log files can have an adverse effect on overall QuickBooks performance, so it’s important to periodically cause the events that trigger a reset of the transaction log file. If you perform a manual backup, it’s important to run the backup with some degree of verification enabled. If you complete the backup without verification enabled, your transaction log file will be reset, and the unverified data in the backup may be unusable.