Steps to follow when upgrading Master Server Operating System

Good Day,

I have to do a Server OS Upgrade on my NetBackup 8.0 Master Server.

Current OS = MS Server 2008 R2 Standard, Sp1 64Bit.

Upgrade to = MS Server 2012 R2 Standard, Sp1 64Bit.

My Backups currently writes to Data Domain via OST Plugin.
 

Please advise the proper steps (Backups / Installation process) I need to take to make sure my Server OS Upgrade / NetBackup Installation runs successfully.

thanks

VIKASH