Mongosync cluster to cluster sync

Hello MongoDB community. I have been doing mongosync cluster to cluster sync. So here is scenario I have prod and staging env. So I need to make backup and restore weekly basis so I am planning to use “mongosync” to do that since it will reduce cost comparatively to mongodump and restore. So i want to resume on saturday mongosync and pause on sunday. but while I was testing I was having an issue on oplog window from mongosync when I have paused it for 3-4 days I could not resume it again. Is there anyone who could help me in this case. so how much oplog window should I set up to cluster?

You should have enough oplog window to cover the time when mongosync is offline + some buffer. In your case sounds like 7-8 days should be a good start

One more question.Is oplog window refreshes within each process. I mean every week when we are making resume process in mongosync the oplog window of 8 days again becomes 8 day or no. So basically within resume command oplog window restarts again?

If you allow mongosync to fully catch up after the resume (i.e. replication lag reported by /progress API goes close to 0) then yes