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Sharding Reference

Sharding Reference¶

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Sharding Methods in the mongo Shell
Sharding Database Commands
Reference Documentation

Sharding Methods in the `mongo` Shell¶

Name	Description
`sh._adminCommand()`	Runs a database command against the admin database, like `db.runCommand()`, but can confirm that it is issued against a `mongos`.
`sh.getBalancerLockDetails()`	Reports on the active balancer lock, if it exists.
`sh._checkFullName()`	Tests a namespace to determine if its well formed.
`sh._checkMongos()`	Tests to see if the `mongo` shell is connected to a `mongos` instance.
`sh._lastMigration()`	Reports on the last chunk migration.
`sh.addShard()`	Adds a shard to a sharded cluster.
`sh.addShardTag()`	Associates a shard with a tag, to support tag aware sharding.
`sh.addTagRange()`	Associates range of shard keys with a shard tag, to support tag aware sharding.
`sh.removeTagRange()`	Removes an association between a range shard keys and a shard tag. Use to manage tag aware sharding.
`sh.disableBalancing()`	Disable balancing on a single collection in a sharded database. Does not affect balancing of other collections in a sharded cluster.
`sh.enableBalancing()`	Activates the sharded collection balancer process if previously disabled using `sh.disableBalancing()`.
`sh.enableSharding()`	Enables sharding on a specific database.
`sh.getBalancerHost()`	Returns the name of a `mongos` that’s responsible for the balancer process.
`sh.getBalancerState()`	Returns a boolean to report if the balancer is currently enabled.
`sh.help()`	Returns help text for the `sh` methods.
`sh.isBalancerRunning()`	Returns a boolean to report if the balancer process is currently migrating chunks.
`sh.moveChunk()`	Migrates a chunk in a sharded cluster.
`sh.removeShardTag()`	Removes the association between a shard and a shard tag.
`sh.setBalancerState()`	Enables or disables the balancer which migrates chunks between shards.
`sh.shardCollection()`	Enables sharding for a collection.
`sh.splitAt()`	Divides an existing chunk into two chunks using a specific value of the shard key as the dividing point.
`sh.splitFind()`	Divides an existing chunk that contains a document matching a query into two approximately equal chunks.
`sh.startBalancer()`	Enables the balancer and waits for balancing to start.
`sh.status()`	Reports on the status of a sharded cluster, as `db.printShardingStatus()`.
`sh.stopBalancer()`	Disables the balancer and waits for any in progress balancing rounds to complete.
`sh.waitForBalancer()`	Internal. Waits for the balancer state to change.
`sh.waitForBalancerOff()`	Internal. Waits until the balancer stops running.
`sh.waitForDLock()`	Internal. Waits for a specified distributed sharded cluster lock.
`sh.waitForPingChange()`	Internal. Waits for a change in ping state from one of the `mongos` in the sharded cluster.

Sharding Database Commands¶

The following database commands support sharded clusters.

Name	Description
`flushRouterConfig`	Forces an update to the cluster metadata cached by a `mongos`.
`addShard`	Adds a shard to a sharded cluster.
`cleanupOrphaned`	Removes orphaned data with shard key values outside of the ranges of the chunks owned by a shard.
`checkShardingIndex`	Internal command that validates index on shard key.
`enableSharding`	Enables sharding on a specific database.
`listShards`	Returns a list of configured shards.
`removeShard`	Starts the process of removing a shard from a sharded cluster.
`getShardMap`	Internal command that reports on the state of a sharded cluster.
`getShardVersion`	Internal command that returns the config server version.
`mergeChunks`	Provides the ability to combine chunks on a single shard.
`setShardVersion`	Internal command to sets the config server version.
`shardCollection`	Enables the sharding functionality for a collection, allowing the collection to be sharded.
`shardingState`	Reports whether the `mongod` is a member of a sharded cluster.
`unsetSharding`	Internal command that affects connections between instances in a MongoDB deployment.
`split`	Creates a new chunk.
`splitChunk`	Internal command to split chunk. Instead use the methods `sh.splitFind()` and `sh.splitAt()`.
`splitVector`	Internal command that determines split points.
`medianKey`	Deprecated internal command. See `splitVector`.
`moveChunk`	Internal command that migrates chunks between shards.
`movePrimary`	Reassigns the primary shard when removing a shard from a sharded cluster.
`isdbgrid`	Verifies that a process is a `mongos`.

Reference Documentation¶

Config Database: Complete documentation of the content of the local database that MongoDB uses to store sharded cluster metadata.

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