Incident note: Nextcloud "file is locked" (423 Locked): fix

Read the signal

Start with the exact wording of the error and its timestamp in the log. Then narrow down the cause before changing anything.

OCP\Lock\LockedException: "files/9a3c1e7d/Dokumente/Bericht.docx" is locked, existing lock on file: exclusive

Narrow down possible causes

• File locking uses the database instead of Redis, and locks stay behind after aborts.
• An aborted upload or desktop client sync; the PHP process was killed by a timeout.
• The file is still open in Collabora or OnlyOffice.
• Background jobs do not run (no system cron), so expired locks are not cleaned up.

Check before changing anything

1. Which locking backend is configured?

   sudo -u www-data php /var/www/nextcloud/occ config:system:get memcache.locking

2. Check that Redis is reachable

   redis-cli ping

3. Count locks in the database (with DB locking)

   mysql -u nextcloud -p nextcloud -e 'SELECT COUNT(*) FROM oc_file_locks WHERE `lock` <> 0;'

4. Check the background job mode

   sudo -u www-data php /var/www/nextcloud/occ config:app:get core backgroundjobs_mode

Fix and test again

1. Use Redis for locking: 'memcache.locking' => '\OC\Memcache\Redis' in config.php.
2. Switch background jobs to system cron: */5 * * * * php -f /var/www/nextcloud/cron.php in www-data's crontab.
3. Clear stale DB locks: maintenance mode on, DELETE FROM oc_file_locks WHERE 1;, maintenance mode off.
4. With Redis, locks expire via TTL; only flush the Redis database in an emergency, and only if Nextcloud is its sole user.

Then repeat the original action and compare the result with the initial error.

Keep a note for the next ticket

Record the exact error, the check result, the change and the retest. That gives the team a useful starting point next time.

Can I just disable file locking?

Technically yes (filelocking.enabled set to false), but you risk corrupted files on concurrent access. Use Redis instead.

Full error guide: Nextcloud: "file is locked" and HTTP 423 Locked