Currently, we allow dropping of oplog on standalone nodes which can lead to undesired behavior (see SERVER-38356). To fix it, we will ban the dropping of oplog entirely on wiredTiger storage engine. But, allow oplog dropping on mmapv1 for stand alone nodes as it doesn't support replSetResizeOplog cmd. To implement this behavior, we are planning to check supportsRecoveryTimestamp() (before dropping of oplog in dbcommands.cpp) as it returns true for WT storage engine regardless of EMRC value and for mmapv1, it returns false.

To implement this in a more cleaner way, it would be good if we have a method in storage interface layer which tells the support of replSetResizeOplog cmd (dynamic oplog resizing) for a storage engine.