LRCAT-SHM and LRCAT-WAL are for ?

[Rob_Cullen]

(Lightroom Classic 7.0.1, WIndows-10)

Why do these files exist in the catalog location?

What is their technical purpose?

I note they are temporary, like the '.LOCK' file, and disappear when Lightroom Classic closes.

[johnrellis · Accepted solution]

These are temporary files created when LR has the catalog database open.  (The database is implemented using SQLite.)  See here for their technical purposes: https://sqlite.org/tempfiles.html

[Rob_Cullen]

Thanks.

Unfamiliar with SQLite and had not seen these files before the recent versions of Lightroom.

[johnrellis]

Reading the SQLite documentation, it may be that LR 7 has moved to the "write-ahead logging" (WAL) provided by newer versions of SQLite, which is supposed to make updates to the database faster.  This would account for why you didn't see these files in older versions of LR.

[shawnw67]

I noticed one of these files appear when doing some testing with a LR Classic CC 7.1 catalog stored in my synced Creative Cloud Files folder, when I had two different synced computers running LR Classic CC at once. Making an edit in one instance of the catalog caused a warning to appear on the other, and a file "Catalog Name (Conflicted copy from ComputerName on 2018-02-03).lrcat-wal" appeared. The file appears to contain all the data associated with the particular image I edited to create the conflict. In another test, the lrcat-wal file was a complete copy of the catalog, so it is clear that having the same catalog open in multiple synced locations is not a good idea. It would be nice if Adobe could find a more elegant way to deal with this, such as warning of the lock file when you launch LR, instead of just creating these WAL files. A better option would be to offer a way to merge conflicts saved in the WAL files, and best would be to offer a true multi user experience with LR...

[johnrellis]

As you've discovered, LR wasn't designed to have two instances concurrently accessing the same catalog.  Over the years, many many people have asked for concurrent access to LR by multiple users and for the ability to access a catalog stored on a network volume.  It's one of the most popular feature requests: Lightroom: Multi-User / Multi Computer (Shared catalog on a network) | Photoshop Family Customer Com... . At this point, though, I think it is highly unlikely this will ever be added to LR Classic -- Adobe has publicly indicated that going forward, they are focusing their efforts on Develop tools and performance, so whatever focus they had on Library before is significantly reduced.

[Vic-86]

OK, this makes perfect sense.

Windows just did an update, and now Lr Classic won't start. I can use file manager and watch as the .lrcat-shm file is created and deleted, created and deleted, over and over. And nothing happens. The computer has been restarted several times, and I have deleted the lock .lrcart-shm and .wal files. Try to start Lr and the pattern repeats, endlessly.

Help

[johnrellis]

I recommend reposting this in a new thread where more people are likely to see it and respond.

[wesleyhuls]

Hey Vic!

How did u manage to solve the problem?

[johnstonanthony]

From what i understand these LRCAT-WAL files are only temporary and present while LR is open. However, even when LR is closed I have multiple LRCAT-WAL files. Is it safe to delete them? They add up to about 8GB of my harddrives space

[bc73436340]

Hello,

I have exactly the same problem with multiple -lock, -shm and -wal files that do not disappear when I close Lightroom.

Did you get a solution about this ? Have you deleted those files ?

Thanks

Bernard

Maoc OS 12.6.3, Lightroom 12.2.1

[Rikk Flohr: Photography]

You’ve posted to a very old thread. It is highly unlikely that the issue described in this thread, though not impossible, is the same issue which you are currently experiencing. Rather than resurrect an old thread that is seemingly similar, you are better posting to a new thread with fresh, complete information including system information, a complete description of the problem and step-by-step instructions for reproduction. 

In the unlikely event the issue is the same, we will merge you back into the appropriate location. 

Thank you!