tencent cloud

Overview

Writing data to the target database when DTS migrates data may cause data inconsistency between the source and target databases. If the read-only target database feature is enabled, DTS will revoke all the write permissions of the target database except for the migration account and prohibit authorization during data migration so as to limit writes to the target database. It will open up write permissions after migration is completed. This helps avoid data inconsistency due to double write.

Note：

To try out this feature, submit a ticket for application.

Notes

As DTS will revoke the write permissions of the target database after the read-only target database feature is enabled, the more the accounts in the target database, the longer the time the task stays in the Preparing and Completed statuses.

Directions

Currently, the read-only target database feature conflicts with the account migration feature. Therefore, if you want to make the target database read-only and migrate accounts, you need to perform two migration tasks as detailed below:

• To enable read-only target database without migrating accounts, directly perform task 2.
• To enable read-only target database and migrate accounts, perform tasks 1 and 2.

Task 1. Account migration

Note：

This section describes only the different steps to set the read-only target database feature. For more information on configuration, including migrated account authorization, operation limits, and notes, see Migration from MySQL to TencentDB for MySQL.

Create an empty test database in the source database. Then, create a full migration task, set Migration Object to Specify object, select Migrate Account, and select the test database. After migrating the accounts in the source database to the target database, complete the task.

1. Create an empty test database in the source database.
2. Log in to the DTS console, select Data Migration on the left sidebar, click Create Migration Task, and enter the Create Migration Task page.
3. On the Create Migration Task page, select the types, regions, and specifications of the source and target databases and click Buy Now.
4. Configure the migration task.
   On the Set source and target databases page, configure the task, source database, and target database settings. After the source and target databases pass the connectivity test, click Create.
   
5. On the Set migration options and select migration objects page, configure the migration type and objects and click Save.

• Migration Type: Select Full migration.
• Data Consistency Check: Select No check.
• Migration Object: Select Specify object and then select the test database.
• Migrate Account: Enable this option.
• Advanced Migration Object:
  

6. On the Verify task page, DTS will check the account information in the source database and will migrate eligible accounts.

   Note：

   For detailed requirements for account migration, see Account Migration.

7. After the task status becomes Completed, create the next migration task.

Task 2. Read-only target database configuration

Migrate objects except accounts and enable read-only target database.

1. Purchase a migration task. On the Create Migration Task page, select the types, regions, and specifications of the source and target databases and click Buy Now.
2. Configure the migration task.
   On the Set source and target databases page, configure the task, source database, and target database settings. After the source and target databases pass the connectivity test, click Create. Here, Access Type needs to be the same as that selected in task 1.
3. On the Set migration options and select migration objects page, configure the migration type and objects and click Save.

• Migration Type: Select as needed.
• Data Consistency Check: Select as needed.
• Migration Object: Select Entire instance.
• Advanced Migration Object: Select as needed.
• Read-Only Target Database: Enable this option.
• Migrate Account: Disable this option.

4. Verify the task.
5. Return to the data migration task list, and you can see that the task has entered the Preparing status. After 1–2 minutes, the data migration task will be started.
   The more the accounts in the target database, the longer the time the task stays in the Preparing and Completed statuses.