Correct – SCCM 2012 does not support SQL Mirroring and can breake a SCCM SP1 upgrade
As stated here SQL mirroring is not supported for the ConfigMgr database. However a technet article do not stop all database administrors’s from enabling the setting anyway believing that it will not cause any issues – but boy it does. SQL mirroring will break the SCCM SP1 upgrade process and leave the primary site server in a non-functional mode where a site restore is the only way back. The issue can be found in the ConfigMgrSetup.log file. USE [cm_ps1]; ALTER DATABASE [cm_ps1] SET SINGLE_USER WITH ROLLBACK IMMEDIATE; $$<Configuration Manager Setup><01-11-2013 10:38:29.887+00><thread=4136 (0x1028)> *** [42000][1468][Microsoft][SQL Server Native Client 11.0][SQL Server]The operation [...]