db.repairDatabase() provides a wrapper around the database command repairDatabase, and has the same effect as the run-time option mongod --repair option, limited to only the current database. See repairDatabase for full documentation.
During normal operations, only use the repairDatabase command and wrappers including db.repairDatabase() in the mongo shell and mongod --repair, to compact database files and/or reclaim disk space. Be aware that these operations remove and do not save any corrupt data during the repair process.
If you are trying to repair a replica set member, and you have access to an intact copy of your data (e.g. a recent backup or an intact member of the replica set), you should restore from that intact copy, and not use repairDatabase.
Changed in version 2.6: The db.repairDatabase() is now available for secondary as well as primary members of replica sets.