You can use this feature to run the Rebuild Indexes command. An index is a database structure created on a table to speed up data retrieval. (For example, searching an indexed column is often much faster than searching a non-indexed column.) SMS uses many indexes to improve database performance. This command creates indexes on database columns that are at least 50% unique, drops indexes on columns that are less than 50% unique, and rebuilds all existing indexes that meet the criteria.
Default Runs on Sunday.
Schedule a Database Maintenance Task
Maintaining a Site Database Overview