return -limits mongod return -limits mongos return -limits mongod mongos 

## 5.3.2 System Collections 

## Synopsis 

MongoDB stores system information in collections that use the <database>.system. $_{*}$namespace , which Mon- goDB reserves for internal use. Do not create collections that begin with system . 

MongoDB also stores some additional instance-local metadata in the local database (page 652), specifically for repli- cation purposes. 

## Collections 

System collections include these collections stored in the admin database: 

admin.system. roles 

New in version 2.6. 

The admin.system.roles (page 291) collection stores custom roles that administrators create and assign to users to provide access to specific resources. 

admin.system. users 

Changed in version 2.6. 

The admin.system.users (page 291) 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 (page 291) collection. 

admin.system. version 

New in version 2.6. 

Stores the schema version of the user credential documents. 

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

<database>.system. namespaces 

Deprecated since version 3.0: Access this data using listCollections . 

The <database>.system.namespaces (page 291) collection contains information about all of the database’s collections. 

<database>.system. indexes 

Deprecated since version 3.0: Access this data using listIndexes . 

The <database>.system.indexes (page 291) collection lists all the indexes in the database. 

<database>.system. profile 

The <database>.system.profile (page 291) collection stores database profiling information. For in- formation on profiling, see Database Profiling (page 215). 

<database>.system. js 

The <database>.system.js (page 291) collection holds special JavaScript code for use in server side JavaScript (page 266). See Store a JavaScript Function on the Server (page 235) for more information. 

