Switch workloads

Switch workloads

1. Wait for the migration instance to reach the Incremental Data Migration stage, and ensure that the latency in the Running Information column is less than 5 seconds.

   Note

   If your migration instance does not have an Incremental Data Migration stage (that is, you did not select Incremental Data Migration for the Migration Types when configuring the instance), the task automatically completes after the initial data migration. Wait for the instance Status to change to Completed.

2. Temporarily stop your application to prevent new data from being written to the source database.

3. Log on to the source database and check the session information to confirm that no new write operations are active.

   Common commands for viewing session information:

   MySQL

   show processlist;

   SQL Server

   select * from sys.dm_exec_connections;

   Oracle

   select sid,serial#,username,program,machine,status from v$session;

   PostgreSQL

   select * from pg_stat_activity;

   Redis

   CLIENT LIST

   MongoDB

   use admin
   db.runCommand({currentOp: 1, $all:[{"active" : true}]})

   Note

   The results will include the connection from the DTS instance to the source database.

4. Pause the migration instance.

   Important

   • Do not resume a paused instance, as this can cause data inconsistency.

   • If your migration instance does not have an Incremental Data Migration stage, skip this step.

   1. Wait for the migration instance latency to drop to 0 milliseconds.

      Note

      • If Auto Refresh is disabled, you can click the refresh icon above the Actions column to update the latency.

      • A latency of 0 may be transient.

      This indicates that all pending data from the source database has been migrated to the destination database.

   2. Wait for another 1 to 3 minutes.

      During this time, the instance latency may fluctuate within a 2-second range.

   3. In the Actions column for the instance, select > Pause Task.

   4. In the Note dialog box, click OK.

   5. Wait for the instance Status to change to Paused.

5. Create a reverse migration instance.

   1. Keep your application stopped.

   2. Remove the write restrictions on the source database.

   3. Create and start a reverse migration instance.

      Important

      • When you configure the instance, select only Incremental Data Migration for the Migration Types.

      • For instructions on how to create an instance, see Migration scenarios.

   4. Wait for the instance Status to change to Running.

6. Switch workloads.

   1. Point your application to the destination database.

   2. Resume application data writes.

   3. Test your application functionality.

Rollback solution

1. Stop your application from writing new data to the database.

2. Switch workloads back to the source database.

3. Resume application data writes.

Next steps

After switching to the destination database and verifying that your application is stable, test all related features. If you find no issues, you can terminate the reverse migration instance. For more information, see terminate a DTS instance.