SCOM 2012 SP1 upgrade fails with error "Failed to set DW upgrade scenario"

Reason:

This can occur if there is an invalid Data Warehouse server name or SRS database instance name in the registry on the Management Server.

Resolution:

To resolve this, verify that the correct Data Warehouse server name and SRS database instance name exist in the registry on the Management Server:

Data Warehouse server name Reg key:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Microsoft Operations Manager\3.0\Setup\DatawarehouseDBServerName

SRS database instance name REG KEY:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Microsoft Operations Manager\3.0\Reporting\SRSInstance

Once its done, you can do the upgrade and should work fine