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New in version 3.2.

Specify a read concern for the db.collection.find() method.

The readConcern() method has the following form:


The readConcern() method has the following parameter:

Parameter Type Description
level string Optional. One of the following read concern modes: "local" or "majority"

To use a read concern level of "majority", you must use the WiredTiger storage engine and start the mongod instances with the --enableMajorityReadConcern command line option (or the replication.enableMajorityReadConcern setting if using a configuration file).

Only replica sets using protocol version 1 support "majority" read concern. Replica sets running protocol version 0 do not support "majority" read concern.

To ensure that a single thread can read its own writes, use "majority" read concern and "majority" write concern against the primary of the replica set.

See also

Read Concern