Notification Server working very slow after changing database

Hi,

I was having both notification server and database in a VM with 13000 endpoints connected to it. My NS version is 7.5 HF3 and I have moved my DB to separate VM with sql server 2012 sp1, previously sql server version was 2008 r2. Now after changing the database my notification server become very slow. The configuration of my old VM and the new VM is same. Can anybody help me how to rectify the slowness issue.