Fix ERROR_NO_LOG_SPACE (0x000003FB) Registry Log Full

Quick answer

Run regedit and increase the LogFileSize value under HKLM\SYSTEM\CurrentControlSet\Control\hivelist, or use reg.exe save to flush pending operations.

Why this happens

The registry logs every change to a hive file — security, software, system, etc. Each hive has a limited transaction log (usually 512 KB). When a process writes faster than the log can flush, or when pending operations pile up after a crash, you hit ERROR_NO_LOG_SPACE (0x000003FB). The system can't allocate more space because the log is full. I've seen this most often after a failed Windows update rollback or a runaway installer like a botched Adobe Creative Cloud update. The log fills, and the registry refuses any new writes — apps crash, services fail to start, and you get that error in the System event log (Event ID 1000 or 160).

Fix steps

1. Back up the registry first. Don't skip this. Export the affected hive via reg export HKLM\SYSTEM C:\backup_system.reg.
2. Open Regedit as Administrator. Go to HKLM\SYSTEM\CurrentControlSet\Control\hivelist. You'll see a list of hive paths (like \??\C:\Windows\system32\config\SYSTEM).
3. Check each hive's log file size. The default is 512 KB for most hives. Create a DWORD value LogFileSize in each hive's key (e.g., under HKLM\SYSTEM\CurrentControlSet\Control\hivelist\SYSTEM and set it to 1048576 (1 MB) in decimal. This forces the log to expand. Reboot.
4. If that doesn't work, use reg.exe save to flush pending operations. Open an elevated command prompt and run:

   reg save HKLM\SYSTEM C:\temp\system.hiv /y

   Then reboot. The /y flag overwrites without prompt. This writes all pending changes to the hive and resets the log.
5. Still stuck? Boot from a Windows Recovery Environment (WinRE) or a Windows install USB. Open Command Prompt and run chkdsk /r C: to fix file system corruption that may be locking the log file. Then run sfc /scannow /offbootdir=C:\ /offwindir=C:\Windows.

Advanced: Manually trim the log

If the hive is bloated (say, the SOFTWARE hive is 800 MB), you need to trim it. Tools like regedit can't delete inside a hive while it's loaded. Use reg.exe unload on a loaded hive (in safe mode with networking), then load it as a temporary hive, delete junk keys, and unload. For example:

reg load HKLM\TempHive C:\Windows\system32\config\SOFTWARE reg delete HKLM\TempHive\Microsoft\Windows\CurrentVersion\Installer\UserData /f reg unload HKLM\TempHive

Alternative fixes if main one fails

• Increase page file size. I've seen a full page file mimic this error. Set it to 1.5x RAM.
• Disable registry caching temporarily. Set HKLM\SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management\LargeSystemCache to 0, reboot.
• Use Sysinternals Process Monitor to find which process is hammering the registry. Filter for RegSetValue and look for high-frequency writes. Kill that process.
• Disk space check. If the drive where the hive lives (usually C:) has less than 1% free, the log can't extend. Free up space.

Prevention tip

Set a GPO to limit registry write rates for non-critical services. Or, if you're on Server 2019+, enable Registry Write Caching via fsutil behavior set registrywritecache 1. This batches writes and reduces log pressure. Also, schedule weekly reboots for machines that run heavy installers (like SCCM clients). The log clears on reboot.