Lock, Unlock, or Create a Private Copy of the Candidate Configuration Using the Junos XML Protocol

To lock the candidate configuration, a client application emits the <lock-configuration/> tag within an <rpc> tag.

Locking the candidate configuration prevents other users or applications from changing the candidate configuration until the lock is released. This is equivalent to the CLI configure exclusive command. Locking the configuration before making changes is recommended, particularly on devices where multiple users are authorized to change the configuration. A commit operation applies to all changes in the candidate configuration, not just those made by the user or application that requests the commit. Allowing multiple users or applications to make changes simultaneously can lead to unexpected results.

The Junos XML protocol confirms that it has locked the candidate configuration by returning an opening <rpc-reply> and closing </rpc-reply> tag with nothing between them.

If the Junos XML protocol server cannot lock the configuration, the <rpc-reply> tag instead encloses an <xnm:error> element explaining the reason for the failure. Reasons for the failure can include the following:

• Another user or application has already locked the candidate configuration. The error message reports the login identity of the user or application.

• The candidate configuration already includes changes that have not yet been committed. To commit the changes, see Committing the Candidate Configuration Using the Junos XML Protocol. To discard uncommitted changes, see Replacing the Configuration Using the Junos XML Protocol.

Only one application can hold the lock on the candidate configuration at a time. Other users and applications can read the candidate configuration while it is locked, or can change their private copies. The lock persists until either the Junos XML protocol session ends or the client application unlocks the configuration by emitting the <unlock-configuration/> tag, as described in Locking and Unlocking the Candidate Configuration or Creating a Private Copy Using the Junos XML Protocol.

If the candidate configuration is not committed before the client application unlocks it, or if the Junos XML protocol session ends for any reason before the changes are committed, the changes are automatically discarded. The candidate and committed configurations remain unchanged.

As long as a client application holds a lock on the candidate configuration, other applications and users cannot change the candidate. To unlock the candidate configuration, the client application includes the <unlock-configuration/> tag in an <rpc> tag:

The Junos XML protocol server confirms that it has successfully unlocked the configuration by returning an opening <rpc-reply> and closing </rpc-reply> tag with nothing between them.

If the Junos XML protocol server cannot unlock the configuration, the <rpc-reply> tag instead encloses an <xnm:error> element explaining the reason for the failure.

To create a private copy of the candidate configuration, a client application emits the <private/> tag enclosed in <rpc> and <open-configuration> tags.

The client application can then perform the same operations on the private copy as on the regular candidate configuration.

After making changes to the private copy, the client application can commit the changes to the active configuration on the device running Junos OS by emitting the <commit-configuration> tag element, as for the regular candidate configuration. However, there are some restrictions on the commit operation for a private copy. For more information, see Committing a Private Copy of the Configuration Using the Junos XML Protocol.

To discard the private copy without committing it, a client application emits the <close-configuration/> tag enclosed in an <rpc> tag element.

Any changes to the private copy are lost. Changes to the private copy are also lost if the Junos XML protocol session ends for any reason before the changes are committed. It is not possible to save changes to a private copy other than by emitting the <commit-configuration> tag element.

The following example shows how to create a private copy of the configuration. The Junos XML protocol server includes a reminder in its confirmation response that changes are discarded from a private copy if they are not committed before the session ends.