As part of the July Patch Tuesday update, Microsoft not only fixed a record number of security vulnerabilities and rolled out some new features, but also patched a fresh bug that caused Windows 11 to waste up to 500 GB of storage space.
The Capability Access Manager bug in question can cause storage space to run low on Windows 11 PCs even when there’s sufficient free space available. A fault in the CapabilityAccessManager.db-wal file causes the system drive to grow increasingly full. This file is linked to the Windows service Capability Access Manager, which in turn is responsible for app permissions in Windows. The file should normally only take up a few MB of storage, but on some PCs it amounts to several hundred GBs.
With update KB5101650, Microsoft has fixed this problem. Unlike the new features in the patch, this fix should work immediately after installation—no gradual rollout. In the patch notes, Microsoft’s entry regarding the bug is remarkably terse:
[Storage] This update improves disk space usage for the CapabilityAccessManager.db-wal file.
Microsoft doesn’t say whether a WAL file that has already grown to several hundred GBs will be automatically reduced in size. According to Windows Latest, users who had installed the optional June update reported that their file was still large even after the update and only returned to normal after they had deleted it manually.
So, after installing update KB5101650, you should check whether your WAL file is still large or has shrunk down. To do this, enter the following in the Windows Command Prompt with administrator rights:
robocopy "C:\ProgramData\Microsoft\Windows\CapabilityAccessManager" "%TEMP%\CAMCheck" /L /B /R:0 /W:0 /BYTES /NP
Alternatively, use an external tool such as WizTree, TreeSize, or WinDirStat to search for the “CapabilityAccessManager.db-wal” file and check its size. If it’s several GB large, you should delete the file using the method described here. (Deleting the file in a way that does not follow the recommended procedure may cause problems.) If the file is only a few hundred KB or a few MB in size, then everything is fine.
