Manual:$wgReadOnlyFile

Maintenance scripts setting: $wgReadOnlyFile
If this file is found, the database is locked for the reason given in the contents of the file.
Introduced in version:Before 1.1.0
Removed in version:Still in use
Allowed values:(path to a file)
Default value:"{$wgUploadDirectory }/lock_yBgMBwiR"
(Note: The default value of this variable depends on other variables, such as the values set in Setup.php , after LocalSettings.php is executed)

Details

If this file is found and its contents are more than 0 bytes long, the database is locked for the reason given in the contents of the file.

The file must be writable by the web server for locking the database when using the special pages "Special:LockDB" (locking) and "Special:UnlockDB" (unlocking).

This feature cannot be used if the wiki uses CACHE_DB for $wgSessionCacheType since users cannot log into the wiki to access "Special:UnlockDB" for unlocking the database.

See also