Data Transmission Service:Synchronize data from a PolarDB for MySQL cluster to a PolarDB-X instance

Prerequisites

• The binary logging feature is enabled for the PolarDB for MySQL cluster. For more information, see Enable binary logging.

• The tables to be synchronized from the source database contain primary keys.

• The destination database has sufficient storage space.

• A PolarDB-X instance is created. For more information, see Create a PolarDB-X 1.0 instance and Create a database.

  Note

  When you create an instance, you must select RDS MySQL as the storage type.

Precautions

• DTS uses read and write resources of the source and destination RDS instances during initial full data synchronization. This may increase the loads of the RDS instances. If the instance performance is unfavorable, the specification is low, or the data volume is large, database services may become unavailable. For example, DTS occupies a large amount of read and write resources in the following cases: a large number of slow SQL queries are performed on the source RDS instance, the tables have no primary keys, or a deadlock occurs in the destination RDS instance. Before data synchronization, evaluate the impact of data synchronization on the performance of the source and destination RDS instances. We recommend that you synchronize data during off-peak hours. For example, you can synchronize data when the CPU utilization of the source and destination RDS instances is less than 30%.

• During initial full data synchronization, concurrent INSERT operations cause fragmentation in the tables of the destination cluster. After initial full data synchronization, the tablespace of the destination cluster is larger than that of the source database. The destination database has sufficient storage space.

• DTS does not synchronize schemas from an ApsaraDB RDS for MySQL instance to a PolarDB-X instance. Before you configure a data synchronization task, you must create databases and tables in the destination instance.

Limits

• You can select only tables as the objects to be synchronized.

• DTS does not synchronize the following types of data: BIT, VARBIT, GEOMETRY, ARRAY, UUID, TSQUERY, TSVECTOR, TXID_SNAPSHOT, and POINT.

• Prefix indexes cannot be synchronized. If the source database contains prefix indexes, data may fail to be synchronized.

• We recommend that you do not use gh-ost or pt-online-schema-change to perform DDL operations on objects during data synchronization. Otherwise, data synchronization may fail.

SQL operations that can be synchronized

INSERT, UPDATE, and DELETE

Permissions required for database accounts

Supported synchronization topologies

• One-way one-to-one synchronization

• One-way many-to-one synchronization

Supported synchronization topologies

• One-way one-to-one synchronization

• One-way many-to-one synchronization

Before you begin

When you synchronize data from a PolarDB for MySQL cluster to a PolarDB-X instance, note that DTS does not support initial schema synchronization. Therefore, you must create databases and tables in the destination instance based on the schemas of the objects in the source PolarDB for MySQL cluster. For more information, see Create a database and Create a table.

Procedure

1. Purchase a data synchronization instance. For more information, see Purchase a DTS instance.

   Note

   On the buy page, set Source Instance to PolarDB, set Target Instance to PolarDB-X, and set Synchronization Topology to One-Way Synchronization.

2. Log on to the DTS console.

   Note

   If you are redirected to the Data Management (DMS) console, you can click the icon in the to go to the previous version of the DTS console.

3. In the left-side navigation pane, click Data Synchronization.

4. In the upper part of the Synchronization Tasks page, select the region in which the destination instance resides.

5. Find the data synchronization instance and click Configure Task in the Actions column.

6. Configure the source cluster and the destination instance.

   

   Section	Parameter	Description
   N/A	Synchronization Task Name	DTS automatically generates a task name. We recommend that you specify an informative name for easy identification. You do not need to use a unique task name.
   Source Instance Details	Instance Type	Select PolarDB Instance.
   	Instance Region	The source region that you selected on the buy page. You cannot change the value of this parameter.
   	PolarDB Instance ID	Select the ID of the source PolarDB cluster.
   	Database Account	Enter the database account of the source PolarDB cluster. For information about the permissions that are required for the account, see Permissions required for database accounts.
   	Database Password	Enter the password of the database account.
   Destination Instance Details	Instance Type	This parameter is set to DRDS Instance and cannot be changed.
   	Instance Region	The destination region that you selected on the buy page. You cannot change the value of this parameter.
   	DRDS Instance ID	Select the ID of the destination DRDS instance.

7. In the lower-right corner of the page, click Set Whitelist and Next.

   Note

   DTS adds the CIDR blocks of DTS servers to the whitelists of the source cluster and the destination instance. This ensures that DTS servers can connect to the source cluster and the destination instance.

8. Select the synchronization policy and the objects to be synchronized.

   

   Setting	Description
   Select the objects to be synchronized	Select one or more tables from the Available section and click the icon to move the tables to the Selected section. Note You can select only tables as the objects to be synchronized. By default, after an object is synchronized to the destination instance, the name of the object remains unchanged. You can use the object name mapping feature to change the names of the objects that are synchronized to the destination instance. For more information, see Rename an object to be synchronized.
   Rename Databases and Tables	You can use the object name mapping feature to rename the objects that are synchronized to the destination instance. For more information, see Object name mapping.
   Retry Time for Failed Connections	By default, if DTS fails to connect to the source or destination database, DTS retries within the next 720 minutes (12 hours). You can specify the retry time based on your needs. If DTS reconnects to the source and destination databases within the specified time, DTS resumes the data synchronization task. Otherwise, the data synchronization task fails. Note When DTS retries a connection, you are charged for the DTS instance. We recommend that you specify the retry time based on your business needs. You can also release the DTS instance at your earliest opportunity after the source and destination instances are released.

9. Click Next.

10. Specify whether you want to perform initial full data synchronization.

    

    Note

    During initial full data synchronization, DTS synchronizes the historical data of the required objects from the source database to the destination database. If you do not select Initial Full Data Synchronization, DTS does not synchronize the historical data.

11. In the lower-right corner of the page, click Precheck.

    Note

    • Before you can start the data synchronization task, DTS performs a precheck. You can start the data synchronization task only after the task passes the precheck.

    • If the task fails to pass the precheck, you can click the icon next to each failed item to view details.

      • After you troubleshoot the issues based on the details, initiate a new precheck.

      • If you do not need to troubleshoot the issues, ignore the failed items and initiate a new precheck.

12. Close the Precheck dialog box after the following message is displayed: Precheck Passed. Then, the data synchronization task starts.

13. Wait until initial synchronization is complete and the data synchronization task enters the Synchronizing state.

    You can view the status of the data synchronization task on the Synchronization Tasks page.