How to Fix 'Failed to Check Session Lock' on Your Minecraft Server

Resolve session.lock errors on your Minecraft Java server caused by unclean shutdowns, multiple instances, or world corruption.

"Failed to check session lock, aborting" means the server tried to acquire exclusive access to a world folder and was refused. Minecraft uses a session.lock file to ensure only one server instance writes to a world at a time — and when something goes wrong with that file, the server refuses to start as a safety measure.

What `session.lock` Does

Every world folder contains a session.lock file. When a server starts:

It opens session.lock and writes a unique value
It keeps the file lock open while running
On clean shutdown, it releases the lock
On the next start, it confirms no other process is holding the lock

If a server is killed (power loss, OOM kill, container restart) instead of stopped cleanly, the lock file may be left in a state the next start can't read — triggering this error.

Why It Happens

Cause	How common
Server killed mid-run (OOM, exit 137, panel kill)	Most common
Two server instances on the same world	Common with cloned servers
Container restart during file write	Sometimes
Filesystem corruption	Rare
Disk full	Rare

Fix It

Make sure no other server is running on this world

Open the XGamingServer Panel Dashboard and confirm only one server is running. If you cloned a server or have multiple instances pointing at the same world, stop all of them.

Critical: Never run two servers on the same world folder. Even briefly. It causes irreversible corruption — chunks get written by both servers and become unreadable.

Stop the affected server

In Console, click Stop. Wait until the Dashboard shows it as fully Offline.

Delete session.lock

Click Files in the sidebar. Open the world folder (world/ by default — or whatever your level-name is). Delete the session.lock file.

If you have separate Nether/End folders (Spigot/Paper format), check world_nether/ and world_the_end/ too — delete session.lock from each.

Safe to delete: session.lock is a runtime lock file. The server recreates it on startup. Deleting it won't affect your world data.

Start the server

Start from Console. The server creates a fresh session.lock and boots normally.

If the Error Comes Back

If session.lock errors keep happening on every restart, you have a deeper issue:

Problem	Fix
Server keeps OOM-killing	Increase RAM — see How Much RAM. Each kill leaves a stale lock
Watchdog kills from `max-tick-time`	Find the lag source with Spark
Two scheduled restarts overlap	Check Schedules for overlapping tasks
World folder corrupted	Restore from Backups, or replace `level.dat` with `level.dat_old`
Disk full	Check the panel storage usage
Filesystem error on host	Open a support ticket — host-side fsck may be needed

Don't Confuse with Other Lock Errors

Error message	What it actually means
`Failed to check session lock`	This guide
`Address already in use`	Network port conflict, not file lock
`Cannot lock storage`	Same root cause as session lock — same fix
`Session lock check failed for world: world`	Same root cause as above

Common Mistakes

Mistake	Fix
Deleting the whole world folder	Only delete `session.lock` — never the world itself
Deleting `session.lock` while the server is running	Stop the server first
Ignoring the underlying crash that left the lock	Find what's killing the JVM and fix that too
Restoring the lock from a backup	Don't — backups shouldn't include `session.lock`

How to Fix 'Failed to Check Session Lock' on Your Minecraft Server

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