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Sharded Cluster Metadata

Config servers store the metadata for a sharded cluster. The metadata reflects state and organization of the sharded data sets and system. The metadata includes the list of chunks on every shard and the ranges that define the chunks. The mongos instances cache this data and use it to route read and write operations to shards.

Config servers store the metadata in the Config Database.


Always back up the config database before doing any maintenance on the config server.

To access the config database, issue the following command from the mongo shell:

use config

In general, you should never edit the content of the config database directly. The config database contains the following collections:

For more information on these collections and their role in sharded clusters, see Config Database. See Read and Write Operations on Config Servers for more information about reads and updates to the metadata.