This action directly clears all registered caches including opcode and dependency injection cache.
Compare and update the database table and field definitions of your installation against the specification defined for every activated extension.
Clears temporary files including concatenated JS/CSS files and processed images.
Resets autoload information for all active third party extensions.
Truncates persistent database tables, which are not related to caching.
Create new administrative users and grant them system maintainer privileges (optional).
Clears preferences and settings for all backend users. The uc field is then set to an empty string.
Download and update language packs for installed extensions.