PolarDB-X is developed by Alibaba Cloud to address the bottleneck of single-host database services.
DRDS is compatible with the MySQL protocol and syntax, and supports automatic sharding,
online smooth scaling, auto scaling, and transparent read and write splitting. DRDS
provides O&M capabilities throughout the lifecycle of databases. This topic describes
how to synchronize data from an ApsaraDB RDS for MySQL instance to a PolarDB-X instance by using Data Transmission Service (DTS).
Prerequisites
- 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 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 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%.
- 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, and TXID_SNAPSHOT.
- 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
Database |
Required permissions |
ApsaraDB RDS for MySQL |
The SELECT permission on the objects to be synchronized, the REPLICATION CLIENT permission,
the REPLICATION SLAVE permission, and the SHOW VIEW permission
|
PolarDB-X |
DTS automatically creates a database account and grants permissions to the account.
You do not need to specify the database account.
|
Supported synchronization topologies
- One-way one-to-one synchronization
- One-way many-to-one synchronization
Before you begin
When you synchronize data from an ApsaraDB RDS for MySQL instance 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 ApsaraDB RDS for MySQL instance. For more
information, see Create a database and Create a table.
Note During schema synchronization, DTS synchronizes the schemas of the required objects from the source database to
the destination database.
Procedure
- Purchase a data synchronization instance. For more information, see Purchase a DTS instance.
Note On the buy page, set Source Instance to MySQL, set Destination Instance to DRDS, and set Synchronization Topology to One-way Synchronization.
- 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 to identify the task. 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.
|
Instance ID |
Select the ID of the source ApsaraDB RDS for MySQL instance. |
Database Account |
Enter the database account of the source RDS instance. For information about the permissions
that are required for the account, see Permissions required for database accounts.
Note If the database engine of the source 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 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 for 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.
|
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. |
- In the lower-right corner of the page, click Set Whitelist and Next.
Note
- You do not need to modify the security settings for ApsaraDB instances (such as ApsaraDB RDS for MySQL and ApsaraDB for MongoDB) and ECS-hosted databases. DTS automatically adds the CIDR blocks of DTS servers
to the whitelists of ApsaraDB instances or the security group rules of Elastic Compute
Service (ECS) instances. For more information, see Add the CIDR blocks of DTS servers to the security settings of on-premises databases.
- After data synchronization is complete, we recommend that you remove the CIDR blocks
of DTS servers from the whitelists or security groups.
- 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 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.
|
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.
|
- Click Next.
- 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.
- 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.
- 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.
