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Internal administrative command. Moves chunks between shards. Issue the moveChunk command via a mongos instance while using the admin database. Use the following forms:


In mongosh, this command can also be run through the sh.moveChunk() helper method.

Helper methods are convenient for mongosh users, but they may not return the same level of information as database commands. In cases where the convenience is not needed or the additional return fields are required, use the database command.

db.adminCommand( { moveChunk : <namespace> ,
find : <query> ,
to : <string>,
forceJumbo: <boolean>,
_secondaryThrottle : <boolean>,
writeConcern: <document>,
_waitForDelete : <boolean> } )


db.adminCommand( { moveChunk : <namespace> ,
bounds : <array> ,
to : <string>,
forceJumbo: <boolean>,
_secondaryThrottle : <boolean>,
writeConcern: <document>,
_waitForDelete : <boolean> } )

The moveChunk command has the following fields:

The namespace of the collection where the chunk exists. Specify the collection's full namespace, including the database name.
An equality match on the shard key that specifies the shard-key value of the chunk to move. Specify either the bounds field or the find field but not both. Do not use the find field to select chunks in collections that use a hashed shard key.
The bounds of a specific chunk to move. The array must consist of two documents that specify the lower and upper shard key values of a chunk to move. Specify either the bounds field or the find field but not both. Use bounds to select chunks in collections that use a hashed shard key.
The name of the destination shard for the chunk.

Optional. A flag that determines if the command can move a chunk that is too large to migrate. The chunk may or may not be labeled as jumbo.

  • If true, the command can move the chunk.

  • If false, the command cannot move the chunk.

The default is false.


The moveChunk command with forceJumbo=true blocks read and write operations on the collection.

This option causes the shard to migrate chunks even when they are larger than the configured chunk size. The collection remains unavailable for the duration of the migration.

To migrate these large chunks without this long blocking period, see Balance Ranges that Exceed Size Limit instead.


Optional. For WiredTiger, defaults to false.

  • If true, then by default, each document move during chunk migration propagates to at least one secondary before the balancer proceeds with the next document. This is equivalent to a write concern of { w: 2 }.

    Use the writeConcern option to specify a different write concern.

  • If false, the balancer does not wait for replication to a secondary and instead continues with the next document.

For more information, see Secondary Throttle.


Optional. A document that expresses the write concern that the _secondaryThrottle will use to wait for secondaries during the chunk migration.

writeConcern requires _secondaryThrottle: true.

Optional. Internal option for testing purposes. The default is false. If set to true, the delete phase of a moveChunk operation blocks.

The value of bounds takes the form:

[ { hashedField : <minValue> } ,
{ hashedField : <maxValue> } ]

The chunk migration section describes how chunks move between shards on MongoDB.


See also:

Only use the moveChunk in special circumstances such as preparing your sharded cluster for an initial ingestion of data, or a large bulk import operation. In most cases allow the balancer to create and balance chunks in sharded clusters. See Create Ranges in a Sharded Cluster for more information.

moveChunk requires that all indexes exist on the target (i.e. to ) shard before migration and returns an error if a required index does not exist.

moveChunk returns the following error message if another metadata operation is in progress on the chunks collection:

errmsg: "The collection's metadata lock is already taken."

If another process, such as a balancer process, changes meta data while moveChunk is running, you may see this error. You may retry the moveChunk operation without side effects.

Starting in MongoDB 5.0, you can set the maxCatchUpPercentageBeforeBlockingWrites to specify the maximum allowed percentage of data not yet migrated during a moveChunk operation when compared to the total size (in MBs) of the chunk being transferred.