# PSMDB oplog format
**URL:** https://forums.percona.com/t/psmdb-oplog-format/4650
**Category:** Percona Server for MongoDB
**Created:** [January 6, 2016, 9:10am UTC](https://forums.percona.com/t/psmdb-oplog-format/4650 "2016-01-06T09:10:01Z")
**Posts on this page:** 4
**Page:** 1
### Author:  [@grumpyguy](https://forums.percona.com/u/grumpyguy)
#### Post date: [January 6, 2016, 9:10am UTC](https://forums.percona.com/t/psmdb-oplog-format/4650/1 "2016-01-06T09:10:01Z")
Using PSMDB with PerconaFT storage engine - what format will the oplog be in? - MongoDB or Tokumx or something else?
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### Author:  [@luis.contreras](https://forums.percona.com/u/luis.contreras)
#### Post date: [January 7, 2016, 8:36am UTC](https://forums.percona.com/t/psmdb-oplog-format/4650/2 "2016-01-07T08:36:07Z")
Hi,
oplog doesn’t change except sizes.
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### Author:  [@grumpyguy](https://forums.percona.com/u/grumpyguy)
#### Post date: [January 7, 2016, 1:48pm UTC](https://forums.percona.com/t/psmdb-oplog-format/4650/3 "2016-01-07T13:48:59Z")
So PSMDB is using standard MongoDB oplog format and Tokumx is still running its own ?
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### Author:  [@jontobs](https://forums.percona.com/u/jontobs)
#### Post date: [January 7, 2016, 2:12pm UTC](https://forums.percona.com/t/psmdb-oplog-format/4650/4 "2016-01-07T14:12:41Z")
grumpyguy,
that’s correct. PSMDB uses the storage engine API that’s available in MongoDB. The storage engine API controls only the data structure used on disk (and memory management). The actual oplog format is controlled higher in the stack, so PSMDB is handed the same oplog information that would be handed to any storage engine.
TokuMX used a modified oplog for several reasons, but the main reason for incompatibility was transactons; GTID was used as the operation identifier instead of timestamp.