Manual:Update.php

checks if the MediaWiki database schema need to be updated in order to work with the current version of MediaWiki. You should run  after each update of MediaWiki or after the update of an extension that requires a schema update (such as CheckUser).

Command line
From the command line, or an SSH shell or similar, change to the maintenance directory and execute the update script: $ php update.php

may exit with errors, leaving the database in an inconsistent state. Always backup the database before running the script!

From the browser
Upgrading docs describe how to run the update script if you do not have access to the command line.

Options

 * --conf: provide configuration settings on the commandline
 * --quick: skip countdown sequence
 * --nopurge: do not purge objectcache table. Normally update.php purges the objectcache table in the database (generally contains the parser cache and the messages cache), if you don't want to purge this table, use the --nopurge option.