I recently setup a simple database mirroring config on my latpop (two instances SQL Server 2005 SP3 etc.).  The databases were configured for HIGH SAFETY but with no witness.  Everything was working fine.  I wanted to simulate a communication failure so I could see the send queue growing.  I just shutdown the mirror instance and then inserted lots of rows into the principal.  Great, so now I executed:

EXEC    sys.sp_dbmmonitorresults @database_name=N'dbm1', 6, 0

But it kept failing with invalid object on dbm_monitor_data.  Looking at sp_dbmmonitorresults I could see that it was failing on line 130.  This was really confusing me so I looked in msdb for the object.  It didn’t exist.

I was suprised to find that the object was only created AFTER launching the database mirroring console.  This creates the necessary monitoring objects in msdb.  Problem solved, after much frustration.