Completion of these steps will free up a lot of resources on an SBS. You will need to have a different method (e.g., Labtech, many others) to keep client machines up to date.

1. Run (install first if not present) the SQL Server Management Studio.
2. Connect the Studio, to type Database Engine, server name \\.\pipe\mssql$microsoft##ssee\sql\query
3. In the Studio, under Databases, you will find an item “SUSDB”.
4. If you don’t know where the database files are held, find them using the properties of that item.
5. Run an SQL query to get a list of connections: EXEC sp_who2
6. Run SQL query/ies to kill all connections to DBName SUSDB only, using the SPIDs, e.g., KILL 999
7. Right-click SUSDB, “Delete” SUSDB, and close the Studio.
8. Delete the database files and all of the update files.
9. Disable the WSUS-related items in services.msc and IIS.

The above is digested from the following:

https://social.technet.microsoft.com/Forums/en-US/d7f5d5bb-6623-4d46-80e6-421674a46829/remove-wsus-from-sbs2011-server?forum=smallbusinessserver

http://blog.mpecsinc.ca/2011/07/sbs-2011-wsus-sql-memory-usage-is-very.html