Thanks Tara. I am watching running queries during that time but also know that sometimes we run batch job and other reports so it might slows down too. I am watching Sql Activity Monitor and see most of the jobs are from replication and we are only subscriber so we don't have any control over publisher. Do you suggest any troubleshooting on subscriber side? Some of the custom Index, I tried to rebuild and updated stats. Mostly I can see user waits while watching WAITSTAT and it's mainly CXPACKET and PAGEIO_LATCH but it's shows up nd goes.
Thanks Tara. I already run Missing Index report also and implemented couple indexes which help but not much as whenever Month Ending process running, it causing lots of Waiting sessions and causing the slow performance issue.