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LRCAT-SHM and LRCAT-WAL are for ?

Adobe Community Professional ,
Nov 09, 2017

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(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.

Regards. My System: Lr-Classic 10.0, Photoshop 22.0, Lightroom 4.0, Windows-10. Nikon DSLR.
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Correct answer by johnrellis | Most Valuable Participant

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

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LRCAT-SHM and LRCAT-WAL are for ?

Adobe Community Professional ,
Nov 09, 2017

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(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.

Regards. My System: Lr-Classic 10.0, Photoshop 22.0, Lightroom 4.0, Windows-10. Nikon DSLR.
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Correct answer by johnrellis | Most Valuable Participant

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

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Nov 09, 2017 1
Most Valuable Participant ,
Nov 09, 2017

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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

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Nov 09, 2017 0
Adobe Community Professional ,
Nov 09, 2017

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Thanks.

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

Regards. My System: Lr-Classic 10.0, Photoshop 22.0, Lightroom 4.0, Windows-10. Nikon DSLR.

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Nov 09, 2017 0
Most Valuable Participant ,
Nov 09, 2017

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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.

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Nov 09, 2017 0
New Here ,
Feb 03, 2018

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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...

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Feb 03, 2018 0
Most Valuable Participant ,
Feb 03, 2018

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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.

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Feb 03, 2018 0
New Here ,
May 17, 2018

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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

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May 17, 2018 0
Most Valuable Participant ,
May 17, 2018

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

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May 17, 2018 0
New Here ,
Oct 12, 2019

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Hey Vic!

 

How did u manage to solve the problem?

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Oct 12, 2019 0
New Here ,
May 01, 2020

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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

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May 01, 2020 1