Database (System) 

Changed in version 14.0

The tool Check and Update Reference Index has been moved to System > Maintenance

This module is only available if the system extension typo3/cms-lowlevel is installed.

The System > Database module offers functions related to the database and its content.

Record Statistics
Shows a count of the various records in the database, broken down by type for pages and content elements.
Search
A tool to search through the whole database. It offers an advanced mode which is similar to a visual query builder.

Some third party extensions offer similar but extended functionality around the database, for example fixpunkt/backendtools can be used during development to find all pages that contain a certain plugin or that use a certain backend layout etc.