System Management Configuration Guide for Cisco 8000 Series Routers, Cisco IOS XR Releases

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System Management Configuration Guide for Cisco 8000 Series Routers, Cisco IOS XR Releases

Commit limits

Updated: June 12, 2026

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Explains how commit limits on Cisco IOS XR routers enable uninterrupted configuration changes by adjusting rebase and ASCII backup operations.

A commit limit is a configuration parameter on Cisco IOS XR routers that

specifies how many configuration changes can be staged before triggering a backup operation,
determines the maximum size of configuration data accumulated before a rebase or backup, and
allows administrators to adjust thresholds to prevent commit interruptions during complex topology changes.

Cisco IOS XR routers use a two-stage configuration model:

Target configuration stage: You build configurations using CLI commands, staging them before applying.
Commit stage: The staged configuration is applied to the router using the commit command, updating the running configuration.

Starting with Release 24.3.1, the rebase operation no longer blocks the commit operation. This allows you to configure complex topology changes without being interrupted by the default blocking of commit changes during the rebase operation. For more information, see the section Concurrent Configuration Rebase during Commit.

Starting with Cisco IOS XR Release 24.2.11, we have made the following enhancements:

You can use the cfs check command to increase the rebase limits in the router from 20 to 40 commits and the configuration data from 2 MB to 4 MB. When configuring the router, you can check the current commit count and configuration data size using the show cfgmgr commitdb command. If the commit count is 20 or higher, or the configuration data size is 2 MB or above, the router will initiate a rebase within 10 seconds. By using the cfs check command to increase the commit count to 40 and the configuration data to 4 MB, you can commit without delay.
You can use the clear configuration ascii inconsistency command to perform an ASCII backup and reset the ASCII backup timer to zero. Once the backup is complete, the router will automatically initiate the next periodic ASCII backup operation only after 55 minutes from the time the clear configuration ascii inconsistency command is executed.

Restrictions for increasing the commit limit

These restrictions apply when increasing the commit limit or managing backups:

The cfs check command increases the rebase limits only for one instance. After the router performs a rebase operation, the limits reset to the default values of 20 commits and 2 MB configuration data. To enable the increased limits again, the cfs check command must be executed again.
If the router reloads after executing the cfs check command, the rebase limits reset to the default 20 commits and 2 MB configuration data.
When the router enters standby mode or reloads, the ASCII backup timer does not reset to zero; the router performs an ASCII backup 55 minutes after the first commit operation before standby or reload.
Cisco does not recommend executing the clear configuration inconsistency and clear configuration ascii inconsistency commands regularly after each commit because these commands cause disk input/output operations that increase hard disk wear and tear.
Frequent execution of these commands leads to frequent hard disk access, which can reduce the hardware lifespan.

Guidelines for increasing the commit limit

Follow these guidelines for increasing the commit limit:

Use the cfs check command to increase the rebase limits from the default 20 commits and 2 MB configuration data to 40 commits and 4 MB configuration data. This allows committing more changes without being blocked by rebase operations.
After executing the cfs check command, the router will perform a rebase operation after 40 commits or when the configuration data reaches 4 MB.
If the router switches over to standby RP after executing the cfs check command, the increased rebase limits (40 commits and 4 MB) are retained.
Use the clear configuration ascii inconsistency command to initiate an ASCII backup and reset the ASCII backup timer to zero. This causes the router to perform the next ASCII backup only after 55 minutes from the command execution.
The ASCII backup merges new commits into the ASCII backup file, and the timer must be reset by executing the clear configuration ascii inconsistency command again before the next 55 minutes if needed.
These commands should be executed only before a commit or sequence of commits that must be done within a specific timeframe and without being delayed by rebase and ASCII backup operations.

Increase the rebase limits

Allow greater flexibility in commit operations by raising the commit count and configuration data limits on the router.

Increasing the rebase limits is useful when you need to maintain a larger commit history or handle larger configuration files, especially in environments where frequent changes are made to device configurations.

Before you begin

Confirm there is sufficient memory available to accommodate increased limits.

Procedure

Confirm there is sufficient memory available to accommodate increased limits.

Example:

Router#cfs check
Creating any missing directories in Configuration File system...OK
Initializing Configuration Version Manager...OK
Syncing commit database with running configuration...OK

Verify that the changes have been applied by viewing the configuration history.

Example:

Router#show configuration history last 5
Sno.  Event      Info                           Time Stamp
~~~~  ~~~~~      ~~~~                           ~~~~~~~~~~
1     cfs check  completed                      Wed Jan 10 11:42:21 2024
2     commit     id 1000000001                  Wed Jan 10 11:39:26 2024
3     startup    configuration applied          Wed Jan 10 11:39:02 2024

The router now supports a higher commit count and larger configuration data size, allowing more configuration versions and larger configuratio

Perform ASCII backup and reset the ASCII backup timer

Backup startup and running router configuration in ASCII format and reset the ASCII backup timer count as a best practice for configuration management.

Performing an ASCII backup ensures a human-readable copy of your current configuration is saved. Resetting the ASCII backup timer may be required after resolving configuration inconsistencies.

Before you begin

Ensure all nodes in the router are in IOS-XR RUN state.
You may check the state of all nodes by running the show platform command.

Procedure

Verify that all nodes are in the RUN state.

Example:

Router#show platform

Confirm all nodes are ready before proceeding.

Perform the ASCII backup and reset the timer.

Example:

Router#clear configuration ascii inconsistency
Router# clear configuration ascii inconsistency
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! Warning: !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!! It is recommended to run this command only when all nodes in router      !!!!
!!!! are in IOS-XR RUN state. To determine node state, run following command: !!!!
!!!! 'show platform'.                                                         !!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! Warning: !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Proceed with the command ?[confirm] y
 Ascii configuration backup is in progress...
Configuration ascii backup complete

It is recommended to run this command only when all nodes in the router are in IOS-XR RUN state. To determine node state, run show platform.

When asked to proceed, confirm by entering y.
The router responds with progress and completion messages
.

(Optional) Verify that the backup and timer reset occurred.

Example:

Router#show configuration history last 5

Look for a backup Periodic ASCII backup event in the recent history.

Your router immediately performs an ASCII backup of the configuration and resets the ASCII backup timer to zero.

Concurrent configuration rebases

A concurrent configuration rebase is a router feature that

allows commit and rebase operations to occur simultaneously,
prevents configuration commits from being blocked during rebase operations, and
enables complex topology changes without interruption.

Before Cisco IOS XR Release 24.3.1, rebase and ASCII backup operations blocked commit actions, requiring manual intervention such as increasing the maximum commit count or resetting the ASCII backup timer. Starting with Release 24.3.1, Cisco IOS XR routers allow concurrent commit and rebase operations, removing the need to use the cfs check command to adjust commit counts or diff sizes. However, ASCII backup operations may still block commits, and the ASCII backup timer can be reset using the clear configuration ascii inconsistency command to minimize downtime.

Table 1. Feature History Table
Feature Name	Release Information	Feature Description
Concurrent Configuration Rebase during Commit	Release 24.3.1	Introduced in this release on: Fixed Systems (8200, 8700); Centralized Systems (8600); Modular Systems (8800 [LC ASIC: Q100, Q200, P100]) The router performs the commit and rebase operations simultaneously, ensuring that the commit operation remains unblocked during the rebase operation. This removes the need to use the cfs check command to increase the commit count and the commit file diff size.

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