MongoDB Documentation, Release 3.0.4 Procedure • Restart the member in standalone mode. • Recreate the oplog with the new size and with an old oplog entry as a seed. • Restart the mongod instance as a member of the replica set. Always use rs.stepDown() to force the primary to become a secondary, before stopping the server. This facilitates a more efficient election process. Restart a Secondary in Standalone Mode on a Different Port Shut down the mongod instance for one of the non-primary members of your replica set. For example, to shut down, use the db.shutdownServer() method: db.shutdownServer() Restart this mongod as a standalone instance running on a different port and without the --replSet parameter. Use a command similar to the following: mongod --port 37017 --dbpath /srv/mongodb Create a Backup of the Oplog (Optional) Optionally, backup the existing oplog on the standalone instance, as in the following example: mongodump --db local --collection 'oplog.rs' --port 37017 Recreate the Oplog with a New Size and a Seed Entry Save the last entry from the oplog. For example, connect to the instance using the mongo shell, and enter the following command to switch to the local database: use local In mongo shell scripts you can use the following operation to set the db object: db = db.getSiblingDB('local') Ensure that the temp temporary collection is empty by dropping the collection: db.temp.drop() Use the db.collection.save() method and a sort on reverse natural order to find the last entry and save it to a temporary collection: To see this oplog entry, use the following operation: db.temp.find() db.temp.save( db.oplog.rs.find( { }, { ts: 1, h: 1 } ).sort( {$natural : -1} ).limit(1 ).next() ) Remove the Existing Oplog Collection Drop the old oplog.rs collection in the local database. Use the fol- lowing command: db = db.getSiblingDB('local') db.oplog.rs.drop() This returns true in the shell. 9.3. Replica Set Tutorials 629 Tip