Create a new client, run insert and remove and inspect the contents of the oplog: var dbWithSession = new Mongo( 'localhost:20000' ).startSession({retryWrites: true }).getDatabase( 'TestDB' ); For inserts: dbWithSession.insert({_id: 1}); The oplog contains lsid/txnNumber information: { "ts" : Timestamp(1508263733, 1), "t" : NumberLong(1), "h" : NumberLong("5813089571967450467"), "v" : 2, "op" : "i", "ns" : "TestDB.TestColl", "ui" : UUID("e551162e-21a0-4c90-82e5-9e6ea239ef1f"), "wall" : ISODate("2017-10-17T18:08:53.938Z"), "lsid" : { "id" : UUID("62f09f8b-5f90-4a5c-9c39-708923793815"), "uid" : BinData(0,"47DEQpj8HBSa+/TImW+5JCeuQeRkm5NMpJWZG3hSuFU=") }, "txnNumber" : NumberLong(0), "stmtId" : 0, "prevOpTime" : { "ts" : Timestamp(0, 0), "t" : NumberLong(-1) }, "o" : { "_id" : 1 } } For removes: dbWithSession.TestColl.remove({_id: 0}); It doesn't: { "ts" : Timestamp(1508263783, 1), "t" : NumberLong(1), "h" : NumberLong("6684227120267171736"), "v" : 2, "op" : "d", "ns" : "TestDB.TestColl", "ui" : UUID("e551162e-21a0-4c90-82e5-9e6ea239ef1f"), "wall" : ISODate("2017-10-17T18:09:43.947Z"), "o" : { "_id" : 1 } }