Thank you for your reply @Tarun_Gaur
I have indeed read the documentation before posting.
I was just surprised to see that upon autoscaling to a M30 instance (because we had a surge of new users) the oplog window kept shrinking instead of autoscaling with the instance.
Before instance upgrade (and the wave of new users), we were on a the minimum instance (M10 I believe?) and we had around 3 days of oplog window.
Our M30 instance has currently 34Go disk free, but the oplog window doesn’t seem to be increasing. It’s like the oplog size doesn’t automatically change and is still at the same initial default value.
That’s why I wanted to set a value myself but I needed guidance on best practice.
Currently and according to real time metrics of Atlas, we have around 90Mo/h written, so that ~2Go/day.
Having 34Go of free disk, it’s not an issue at all.
However, if I specify 2 days of oplog window, that means 4Go of available logs, but what happens if the disk has less than 4Go? Do I receive a warning? Does the server crash or maybe oplog will automatically shrink to the remaining disk space?
Best,
Jerome