Data Transmission Service:Change the current offset of a data synchronization or migration instance

Background information

The current offset is the timestamp of the latest data written to the destination instance. DTS lets you change the Current Offset in the Incremental Write module of a data synchronization or migration instance. The incremental task then starts from the time that you specify on the destination instance.

Scenarios

• To re-apply data changes from the source database that occurred between a specific time and the current offset, you can adjust the offset backward to that specific time. This re-applies the data changes for that period during the Incremental Write phase.

• To skip data changes from the source database that occurred after the current offset, you can adjust the offset forward. This action skips the data changes for that period during the Incremental Write phase.

• If a task fails to retry because the offset does not exist, you can adjust the offset forward to resume the instance.

Prerequisites

• A data synchronization or migration instance that includes an incremental task is created. For more information, see the configuration topics in Overview of data synchronization solutions or Overview of data migration solutions.

• The instance has entered the Incremental Write phase, and its Status is not Modifying Objects.

Impacts

• If you specify a new offset that is later than the current incremental write offset, data changes within this time period are not synchronized to the destination instance. This may cause data loss or inconsistency. Proceed with caution.

• If you specify a new offset that is earlier than the current incremental write offset, data changes within this time period are re-executed on the destination instance. Re-executing INSERT and DDL operations may cause data duplication conflicts. Proceed with caution.

• If the instance is in a paused state, it automatically resumes after you change the offset.

• If you change the task offset to a time before table objects were added using the Reselect Objects operation, data loss occurs. For example:

  1. The Incremental Data Collection task is processing data from time A to time B.

  2. At time C, you use Reselect Objects to add table1 to the sync task.

  3. Warning: If you use Modify Incremental Write Offset to change the offset to time D, data for the new table table1 between time D and time C is not synchronized.

  

Usage notes

• You cannot change the offset for data synchronization or migration instances where both the source and destination are Tair/Redis instances.

• You cannot change the offset of a data synchronization instance if its Status is Modifying Objects.

• If you change the offset of a distributed instance, the change takes effect only on the current subtask.

• The selectable range for a new offset is the last seven days by default. This range can vary based on factors such as the runtime of the Incremental Write module and the instance latency.

Procedure

1. Go to the data synchronization or migration task list page.

   From the DTS console

   1. Log on to the Data Transmission Service (DTS) console.

   2. In the navigation pane on the left, click Data Synchronization or Data Migration.

   3. Optional: In the upper-left corner of the page, select the region where the instance resides.

   From the DMS console

   Note

   The actual steps may vary depending on the mode and layout of DMS. For more information, see Simple Mode console and Customize the layout and style of the DMS console.

   1. Log on to the Data Management (DMS) service.

   2. In the top menu bar, choose Data + AI > Data Transmission (DTS) > Data Synchronization or Data + AI > Data Transmission (DTS) > Data Migration.

   3. Optional: To the right of Data Synchronization Tasks or Data Migration Tasks, select the region where the instance resides.

2. In the Actions column for the destination instance, choose > Pause Task.

3. Click the ID of the destination data synchronization or migration instance to open the instance details page.

4. In the navigation pane on the left, click Task Management. In the Progress section, click the Incremental Write module.

5. Change the instance offset:

   1. On the Basic Information tab, click Change Offset to the right of Current Offset.

   2. Read the Precautions and click Next.

   3. In the Modify Incremental Write Offset dialog box, click the Offset text box and select a date and time for the new offset from the available range.

   4. In the Modify Incremental Write Offset dialog box, click OK.

   5. In the Note dialog box, click OK.

6. View the result.

   After the instance completes initialization, check the Current Offset on the Basic Information tab of the Incremental Write module.

   Note

   • You can click the icon to refresh the page and check the initialization progress and the Current Offset.

   • After the Current Offset is updated, use the data validation feature to verify that the data meets your expectations. For more information, see Configure data validation.