The Database Performance Tool is used to monitor the size of your database, and to manage the index fragmentation percentage of the individual tables. Fragmented indexes can cause database operations to slow down considerably, in much the same way that disk fragmentation causes your computer to run slower.
Click Check for fragmented tables to begin. This may take a considerable amount of time (up to a few minutes), depending on how many records are in your database.
The validation phase executes the SQL Server commands
DBCC CHECKCATALOG, and
DBCC CHECKDB. These commands check the integrity of all constraints in the database, check for consistency in and between system tables in the database, and check the allocation and structural integrity of all the objects in the database.
The compacting phase executes the SQL Server command
DBCC SHRINKDATABASE, which shrinks the size of the data files in the database. Note that no compression is used; the database is simply compacted by removing empty space.
For more information on validating or compacting the database, see Getting Started with SQL Server on the Microsoft Web site..