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max-db-size (Enhanced Subscriber Management)

Syntax

Hierarchy Level

Description

Specify the maximum amount of system shared memory that is available for the Junos OS configuration database and the schema database, together. Starting in Junos OS Release 20.1R1, Junos OS uses a single memory map for both the configuration and schema databases.

In Junos OS Release 19.4Rx and lower-numbered releases, this statement specifies the maximum amount of system shared memory that is available for only the Junos OS configuration database

JUNOS OS processes map shared memory into their process space. For example, on MX240 through MX10003 routers, processes can map up to 1GB of shared memory. Enhanced subscriber management processes contend for shared memory with the JUNOS OS configuration database. Shared memory that is not assigned to the configuration database is automatically available to enhanced subscriber management. By default, the configuration database tries to reserve 80 percent of the shared memory map, leaving insufficient space for subscriber management to function.

The majority of configurations require much less than 300MB of mapped space. An appropriate database size enables subscriber management to operate and scale optimally. In some circumstances, you must limit the size of the database to increase the amount of shared memory available to subscriber management. In other circumstances, we recommend that you allow the router to determine the appropriate size and that you do not configure a maximum size.

  • For MX5, MX10, MX40, MX80, and MX104 routers, you must always configure the maximum size to be no more than 100MB, regardless of the which Junos OS release is running and regardless of Routing Engine RAM.

  • For MX204, MX240, MX480, MX960, MX2008, MX2010, MX2020, and MX10003 routers, the decision whether to explicitly configure a maximum size and what that size is, depends on the Junos OS release and the amount of RAM in the Routing Engines.

    The max-db-size is an optional configuration command on routers having >=32 GB DRAM, for example, on MX960 platform. To enable subscriber-management, use the command set chassis network-services enhanced-ip and set system services subscriber-management enable. The router reboots and comes-up with subscriber-management enabled without max-db-size (optional) configuration and requires only 1 reboot.

  • Junos OS Release

    Routing Engine RAM

    Recommendation

    Release 17.4R1 and earlier releases

    Release 18.1R1

    Any

    Configure maximum size to no more than 300MB.

    Release 17.4R2 and higher 17.4x releases

    Release 18.1R2 and higher releases

    Routing Engines have at least 32GB each

    Allow the router to determine the appropriate size. Do not configure a maximum size.

    Release 17.4R2 and higher 17.4x releases

    Release 18.1R2 and higher releases

    Routing Engines have less than 32GB each

    Configure maximum size to no more than 300MB.
Best Practice:

You must reboot the device before a change in max-db-size value takes effect. By setting this value as part of your initial configuration, you can avoid multiple reboots.

Options

size

Specifies the portion of system shared memory, in megabytes (MB), that is allocated for the Junos configuration database.

  • Syntax: size M to specify MB

  • Default: 698,343,424 bytes, only when running Junos OS Release 17.4R1, enhanced IP network services and enhanced subscriber management are enabled, and both Routing Engines in the chassis have at least 32 GB of RAM. Otherwise, there is no default value.

Required Privilege Level

admin—To view this statement in the configuration.

admin-control—To add this statement to the configuration.

Release Information

Statement introduced in Junos OS Release 15.1R3.

Related Documentation