Hi,

I had to upgrade the SCOM 2012 SP1 to SCOM 2012 R2 .

for this I have deployed SCOM 2012 R2 in same Environment with different Management Group name and Different DBs.

POST SCOM 2012 R2 deployment i have deployed the SCOM 2012 R2 Agent through Console, so Now every Agent Managed Servers/Client Machines has to MG Assigned .

SO what i am looking here is what are the steps now i have to follow to completely De- commission the Old SCOM 2012 SP1 Infra??

This can be scripted:

http://blogs.technet.com/b/scom_atlas/archive/2013/11/22/removing-multiple-mgs-from-your-dual-triple-quad-homed-agents.aspx

http://www.bictt.com/blogs/bictt.php/2012/05/06/manipulating-scom-2012-agent-multihoming

1) make sure that all SCOM agent manged servers/client should report to SCOM 2012 R2 managment group only. This means you should remove multi-home server/clients. Removing SCOM Management Groups from your dual, triple, quad-homed agents, pls. refer to
http://blogs.technet.com/b/scom_atlas/archive/2013/11/22/removing-multiple-mgs-from-your-dual-triple-quad-homed-agents.aspx
2) Decommision SCOM 2012 sp1 MS, DB server
a) Uninstall Core Components
b) If you have deployed the AD Management Pack then there are OpsMgrLatencyMonitors container in AD - SCOM does create items in AD.
c) If you have the Exchange 2007 MP installed (in fact almost any version of Exchange) then test user accounts have likely been created.
d) You have almost certainly used Run As Accounts - the underlying windows accounts needs to be removed. You might have SQL logins created specifically for SCOM that need to be removed from the SQL Servers.
e) If you have network monitoring configured then the network devices will have been congiured to allow SNMP gets from the Management Server(s) in the resource pool.
https://technet.microsoft.com/en-us/library/dn249707.aspx?f=255&MSPPError=-2147217396
Roger