Check Database Size

There is a standard SQL report that shows how much space a database is using. In SQL Server Management Studio for SQL Server 2008 R2 and newer, right-click on the database you are interested in and select Reports->Standard Reports->Disk Usage.

There is a good description of this report, including information about how to resize a Operations Manager database in the SCOMfaq.ch blog: http://blog.scomfaq.ch/2012/06/26/scom-check-size-of-databases-sql-standard-reports/