Check filesystem usage.
If /var is showing 100% full then check actual usage of /var
du -h -x /var|tail -1 ---> It will show actual usage of /var
Check for deleted files which are getting accessed. If actual usage of /var is less than showing in “df -h” command then there must be issue with open log files which are deleted but still accessed by Process.
Check for deleted files which are getting accessed.
lsof | grep "/var" | grep deleted
You will also get process id accessing that files. Just kill or stop these processes. And now check filesystem usage, it should show normal.