Pause phase

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When continuous data synchronization is paused, the Migrate While Active user is directing the Migration Manager to stop migrating changed objects from the source to the copy node.

While the migration phase remains PAUSED, changes to objects are tracked on the source node but none of the changed objects will be migrated to the copy node. Migration will remain paused until continuous data synchronization is started once again.

A pause can be user-initiated or system-initiated.

User-initiated pause

One reason to pause data synchronization is for performing a maintenance action on the source node that requires an IPL or bringing the source node into a restricted state. In preparation for such maintenance, it is recommended that the data synchronization stage be paused prior to proceeding with the maintenance. This is considered a user-initiated pause.

Pausing data synchronization is initiated by clicking the Pause button in the Db2® Mirror GUI as shown in Figure 1.

From the Step 3 Continuous Data Synchronization panel of the IBM i Migrate While Active Guide in the Db2 Mirror GUI, click the Pause button to pause data synchronization.

Figure 1. Step 3 Continuous Data Synchronization pause action
A pause can also be initiated by calling the CHANGE_MIGRATION_MANAGER procedure directly by running the following SQL statement on the source node:
```
CALL QSYS2.CHANGE_MIGRATION_MANAGER(ACTION=>'PAUSE');
```
After the Pause button has been clicked, the Step 3 Continuous Data Synchronization panel shows pausing data synchronization has been requested. Each of the synchronization jobs is notified to stop migrating changed objects from the source to the copy node.

Figure 2. Step 3 Continuous Data Synchronization pause requested

When every synchronization job has completed its current set of object migrations, the Pause phase will be achieved. Information about each synchronization job is displayed until the job completes its migration and its status is changed to Synchronization paused.

Figure 3. Step 3 Continuous Data Synchronization paused jobs
After all the synchronization jobs pause their migration, Step 3 Continuous Data Synchronization of the IBM i Migrate While Active Guide indicates that data synchronization is Inactive because synchronization is paused.

Figure 4. Step 3 Continuous Data Synchronization paused

System-initiated pause

The health center feature within Db2 Mirror continuously monitors the Db2 Mirror environment. When an issue affecting the ability to perform data synchronization is detected, such as an unplanned outage, the health center informs Migrate While Active to execute a system-initiated pause. When a system-initiated pause is performed, the IBM i Migrate While Active Guide in the Db2 Mirror GUI shows Figure 2.

For more information on unplanned outages within the Db2 Mirror environment, see Managing unplanned outages.