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Part of your QuickBooks company data is the TLG file. It’s not something you normally are aware of, but in some situations it can be a very important file.
The transaction log file (TLG for short) is maintained automatically by QuickBooks as part of your data. The file resides in the same folder as your main QBW file, and has the same file name. But it has a .TLG extension. In transaction-intensive businesses, the file can become quite large — 1GB or bigger.
Whenever you post a transaction in your company file, the TLG file is updated. And that is why it is sometimes a very valuable file.
We sometimes talk to people who have lost their current data file — it either got deleted somehow, or is so badly damaged it is unusable and unfixable.
But if they have a good backup — even if it is old — and a good current TLG file, we can take the old backup and bring it to current status by applying the missing transactions we can get out of the TLG file.
It’s one method we use for QuickBooks data repair.
I am working with a customer today who has this exact scenario, so I thought I’d briefly write about it.
p.s. We occasionally hear of users being instructed to delete their TLG file. Don’t ever do that without copying it to a different folder or drive first. You might need it sometime!
I have noticed that even if you do delete the TLG file QuickBooks will re-create it. Does it re-create the file with all of the old transactions or just the ones you have entered since the last time you deleted it?
Hi, Seth! Yes, QB will create a new TLG file if the existing one is deleted, but the new file will contain only transactions entered after it is recreated — the old stuff is gone for good. That’s why I recommend that it not be deleted, but if it must be deleted, save it off to a different location first.
Rather than deleting your .TLG file, you can reduce its size by backing up your company file. I believe that the transaction log file is added back to the company file. I just tried it on my company file. I recommend to my clients in the Seattle area that I set up, review, and train in QuickBooks to do this on a weekly basis. Also, backing up verifies the data.
Keith, my understanding is that if you make a verified backup in QuickBooks, QuickBooks deletes the TLG file. I suppose the thinking is that if the verify is OK then there would be no need for the TLG. But that doesn’t account for the possibility of future problems, where sometimes it would be desirable to have a TLG that goes way back.
If you make a backup without verifying, QB leaves the TLG file alone.
I don’t think that when one makes a verified backup, QuickBooks deletes the TLG file. When I did my backup, QuickBooks didn’t delete my TLG file. It just got smaller.
I always make a complete backup and advise my customers to do the same. That way if there is a problem in the company file, it will be detected during the backup process and the client can then fix it or rebuild their company file.
I am wondering if the purpose of the TLG file is to store transactions between complete or verified backups. Which can then be used to repair a company file.
Keith, you are right — it doesn’t delete the TLG file. But it deletes the previous information in the file and leaves it essentially empty. Pretty much the same end result. The only use I know of for the TLG file is like you say: a way to recover from a data corruption episode.
You might be interested in Charlie Russell’s analysis of this topic.
If the rebuild and verify data goes through successfully do I still need the tog file?
Mark, that’s the tricky thing…you don’t need the TLG file when everything is working right. It’s potentially later, when verify/rebuild would fail, that having an uninterrupted TLG file can come in handy. Particularly if, for some reason, you don’t have a good current backup.