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Database Manual

Reference

System Collections

Synopsis

MongoDB stores system information in collections that use the <database>.system.* namespace, which MongoDB reserves for internal use. Do not create collections that begin with system.

MongoDB also stores some additional instance-local metadata in the local database local.replset.* namespace, specifically for replication purposes and in the config database for sessions information.

Collections

System collections include these collections stored in the admin database:

admin.system.roles: The admin.system.roles collection stores custom roles that administrators create and assign to users to provide access to specific resources.

admin.system.users: The admin.system.users collection stores the user's authentication credentials as well as any roles assigned to the user. Users may define authorization roles in the admin.system.roles collection.

admin.system.version: The admin.system.version collection stores metadata to support internal operations. Do not modify this collection unless specifically instructed to in this documentation or by a MongoDB support engineer.

System collections include these collections stored in the config database:

config.system.indexBuilds: The indexBuilds collection stores information related to in-progress index builds.

Database-Specific Collections

System collections also include these collections stored directly in each database:

<database>.system.buckets

Stores the underlying data associated to a time series collection. The system.buckets collection stores data in an optimized format and schema for an efficient representation of the persisted time series data.

Do not modify this collection.

<database>.system.profile: The <database>.system.profile collection stores database profiling information. For information on profiling, see Database Profiler.

<database>.system.js: The <database>.system.js collection stores special JavaScript code for use in server side JavaScript. See Store a JavaScript Function on the Server for more information.

<database>.system.views

The <database>.system.views collection contains information about each view in the database.

Starting in MongoDB 5.0, for featureCompatibilityVersion set to "5.0" or greater, users can no longer write directly to the <database>.system.views collection.

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