Welcome to the MongoDB community @Mohzim_Shaikh !
The procedure you linked to is for changing the size of the replication oplog.
I suspect the issue you are experiencing is due to:
-
use of an arbiter which cannot acknowledge writes
-
secondary member down for an extended period of time which can cause the primary oplog to grow past the configured size limit:
Starting in MongoDB 4.0, the oplog can grow past its configured size limit to avoid deleting the
majority commit point.
There are two suggestions to avoid this issue:
-
Replace your arbiter with a secondary (see Replica set with 3 DB Nodes and 1 Arbiter - #8 by Stennie_X for more background on why).
-
Disable Read Concern Majority for your PSA deployment to prevent storage cache pressure when a data bearing node is down.
Regards,
Stennie