This topic describes how to synchronize data between ApsaraDB RDS for MySQL instances that belong to different Alibaba Cloud accounts by using Data Transmission Service (DTS).
- The source and destination ApsaraDB RDS for MySQL instances are created. For more information, see Create an ApsaraDB RDS for MySQL instance.
- The database type of the source and destination RDS instances is MySQL.
- The source and destination ApsaraDB RDS for MySQL instances have internal endpoints.
- DTS uses read and write resources of the source and destination databases during initial full data synchronization. This may increase the loads of the database servers. If the database 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 database, the tables have no primary keys, or a deadlock occurs in the destination database. Before you synchronize data, evaluate the impact of data synchronization on the performance of the source and destination databases. 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 databases is less than 30%.
- The tables to be migrated in the source database must have PRIMARY KEY or UNIQUE constraints and all fields must be unique. Otherwise, the destination database may contain duplicate data records.
- During initial full data synchronization, concurrent INSERT operations cause fragmentation in the tables of the destination instance. After initial full data synchronization, the tablespace of the destination instance is larger than that of the source instance.
Supported synchronization typologies
- One-way one-to-one synchronization
- One-way one-to-many synchronization
- One-way cascade synchronization
- One-way many-to-one synchronization
For more information about synchronization topologies, see Synchronization topologies.
SQL operations that can be synchronized
|Operation type||SQL statements|
|DML||INSERT, UPDATE, DELETE, and REPLACE|
- Incompatibility with triggers
If you select a database as the object to be synchronized and the database contains a trigger that updates a table, data inconsistency may occur. For more information about how to solve this issue, see Configure a data synchronization task for a source database that contains a trigger.
- Limits on RENAME TABLE operations
RENAME TABLE operations may cause data inconsistency during synchronization. For example, if only Table A needs to be synchronized and it is renamed Table B, Table B cannot be synchronized to the destination database. To prevent this situation, you can select the entire database where Table A is located as the object when you configure the data synchronization task.
Before you begin
Set the Alibaba Cloud account that owns the destination RDS instance as a trusted account. This allows DTS to access the cloud resources of the Alibaba Cloud account that owns the source RDS instance. For more information, see Configure RAM authorization for cross-account data migration and synchronization.
- Purchase a data synchronization instance by using the Alibaba Cloud account that owns
the destination RDS instance. For more information, see Purchase a data synchronization instance.
Note Select MySQL for both the source instance and the destination instance. Select One-Way Synchronization as the synchronization topology.
- Use the Alibaba Cloud account that owns the destination RDS instance to log on to the DTS console.
- In the left-side navigation pane, click Data Synchronization.
- At the top of the Synchronization Tasks page, select the region where the destination instance resides.
- Find the data synchronization instance and click Configure Synchronization Channel in the Actions column.
- Configure the source and destination instances.
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 RDS Instance. Instance Region The source region that you selected on the buy page. You cannot change the value of this parameter. Alibaba Cloud Account ID of RDS Instance Enter the ID of the Alibaba Cloud account that owns the source RDS instance.Note Before you configure this parameter, click RDS Instances of Other Alibaba Cloud Accounts in the Source Instance Details section. Role Name Enter the name of the RAM role that you configured earlier in Before you begin. RDS Instance ID Select the ID of the source RDS instance. Destination Instance Details Instance Type Select RDS Instance. Instance Region The destination region that you selected on the buy page. You cannot change the value of this parameter. Instance ID Select the ID of the destination RDS instance. Database Account Enter the database account of the destination RDS instance.Note If the database engine of the destination RDS instance is MySQL 5.5 or MySQL 5.6, you do not need to configure the database account or database password. Database Password Enter the password of the destination database account. Encryption Select Non-encrypted or SSL-encrypted. If you want to select SSL-encrypted, you must enable SSL encryption for the RDS instance before you configure the data synchronization task. For more information, see Configure SSL encryption on an ApsaraDB RDS for MySQL instance.Notice The Encryption parameter is available only for regions in the Chinese mainland and the China (Hong Kong) region.
- In the lower-right corner of the page, click Set Whitelist and Next.
- Select the synchronization policy and the objects to be synchronized.
Setting Description Select the objects to be synchronized
Select one or more objects from the Available section and click the icon to move the objects to the Selected section.
You can select tables or databases as the objects to be synchronized.Note
- If you select a database as the object to be synchronized, all schema changes in the database are synchronized to the destination database.
- By default, after an object is synchronized to the destination database, the name of the object remains unchanged. You can use the object name mapping feature to rename 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.
Replicate Temporary Tables When DMS Performs DDL OperationsIf you use Data Management (DMS) to perform online DDL operations on the source database, you can specify whether to synchronize temporary tables generated by online DDL operations.
- Yes: DTS synchronizes the data of temporary tables generated by online DDL operations.
Note If online DDL operations generate a large amount of data, the data synchronization task may be delayed.
- No: DTS does not synchronize the data of temporary tables generated by online DDL operations.
Only the original DDL data of the source database is synchronized.
Note If you select No, the tables in the destination database may be locked.
Retry Time for Failed ConnectionsBy 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.
- In the lower-right corner of the page, click Next.
- Configure initial synchronization.
- During an initial synchronization, DTS synchronizes the schemas and data of the required objects from the source instance to the destination instance. The schemas and data are the basis for subsequent incremental synchronization.
- Initial synchronization includes initial schema synchronization and initial full data synchronization. In most cases, you need to select both Initial Schema Synchronization and Initial Full Data Synchronization.
- In the lower part of the page, click Next: Precheck and Start Task.
- Before you can start the data synchronization task, a precheck is performed. 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.
- You can troubleshoot the issues based on the causes and run a precheck again.
- If you do not need to troubleshoot the issues, you can ignore failed items and run a precheck again.
- Close the Precheck dialog box after the following message is displayed: The precheck is passed. Then, the data synchronization task starts.
- Wait until the initial synchronization is complete and the data synchronization task
is in the Synchronizing state.
You can view the status of the data synchronization task on the Synchronization Tasks page.