Actually I have created 3 node replica Set and in that I have set oplog min time retention period 48hr and oplog size 8GB in each node (my disk size is 100gb). When oplog size is getting full then it is deleting old entries and as we know secondary node copy the oplog of primary to replicate data.
So, my question is that if old entries already deleted from oplog of prim and when we add new secondary node then how it will replicate or sync entire data.