STATUS_LOG_PINNED_RESERVATION (0xC01A0030) Fix

Quick Answer

Restart the service or app that's holding the log reservation (usually a backup tool or database). If that fails, reboot the machine. For stubborn cases, use fsutil to check the log state and force a truncation.

What's Going On?

This error code—0xC01A0030—shows up when a log file gets pinned because a single reservation is hogging almost all the log space. Think of it like this: the Common Log File System (CLFS) in Windows allocates a chunk of space for a client to write to. If that client reserves a huge chunk and never releases it, the log can't be trimmed. The result? Operations that need log space fail with this error.

You'll see this most often with backup software (like VSS writers), SQL Server, or Exchange. I've also seen it triggered by a misbehaving Volume Shadow Copy service. The system event log will usually have a CLFS source event with this code.

Fix Steps

Step 1: Identify What's Holding the Reservation

1. Open an administrative Command Prompt or PowerShell.
2. Run this command to list all active log reservations:
   

   fsutil clfs list-reservations

3. Look for an entry with a high number under "ReservedBytes"—that's your culprit. The output shows the log file path and the client using it.

Step 2: Force a Log Truncation

1. If the log file path is something like C:\Windows\System32\LogFiles\, try this to force the log to shrink:
   

   fsutil clfs truncate <log-file-path>

   
   Replace <log-file-path> with the actual path from step 1. For example: fsutil clfs truncate C:\Windows\System32\LogFiles\MyLog.blf.
2. If you get an access denied error, the log is still in use. Move to step 3.

Step 3: Restart the Related Service

1. From the reservation list, note the client name. Common ones include:
   
   • Microsoft® Volume Shadow Copy Service → restart the Volume Shadow Copy service.
   • Microsoft® SQL Server → restart the SQL Server (MSSQLSERVER) service.
   • Microsoft® Exchange Server → restart the Microsoft Exchange Information Store service.
2. Open Services.msc, find the service, right-click it, and choose Restart.
3. After restart, run fsutil clfs list-reservations again. The reservation should be gone. If not, reboot.

Step 4: Reboot the System

If restarting the service doesn't clear the lock, a full reboot will. After the machine comes back up, check your application—the error should be gone.

Alternative Fixes If the Main Steps Fail

Check VSS Writers

Sometimes a VSS writer gets into a bad state and pins the log. Run this command to list writers:

vssadmin list writers

If any writer shows a state other than "Stable" or "Waiting for completion", reboot the Volume Shadow Copy service or run vssadmin delete shadows /all to clear shadow copies (be careful—this nukes all restore points).

Increase Log Size (Last Resort)

If the application keeps doing this and you can't fix the root cause, you can increase the maximum log size so reservations don't eat up 100%. But this hides the problem. Use fsutil clfs set-quota <log-file-path> <new-size-in-bytes> to bump it up. I don't recommend this unless you're desperate—fix the app instead.

Check Third-Party Backup Software

Tools like Veeam, Acronis, or Symantec Backup Exec can hold log reservations. Restart their services or disable the backup job temporarily to see if the error clears.

Prevention Tips

• Keep backup software updated—old versions often leak log reservations.
• Monitor log space with a simple script that runs fsutil clfs list-reservations daily and alerts you if any reservation exceeds 80% of the log size.
• Avoid running multiple backup jobs that target the same volume at the same time—they fight over log reservations.
• If you're a developer writing code that uses CLFS, test reservation releases aggressively. A forgotten ReserveAndAppendLog call can pin a server.

This error is annoying but it's almost always a single app being greedy. Kill that reservation, and you're back in business.