This topic describes how to synchronize incremental data from a DRDS instance to a PolarDB for MySQL cluster by using Data Transmission Service (DTS).
- A DRDS instance is created. For more information, see Create a instance and Create a database.
Note The storage type of the DRDS instance must be ApsaraDB RDS for MySQL (private custom RDS instances or purchased RDS instances). PolarDB for MySQL cannot be used as the storage type.
- The destination PolarDB for MySQL cluster is created. For more information, see Purchase a pay-as-you-go cluster and Purchase a subscription cluster.
- The available storage space of the destination cluster is larger than the total size of the data in the source instance.
|Limits on the source database||
|Synchronization type||Task configuration fee|
|Schema synchronization and full data synchronization||Free of charge.|
|Incremental data synchronization||Charged. For more information, see Pricing.|
Supported synchronization topologies
- 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 statement|
|DML||INSERT, UPDATE, and DELETE|
Permissions required for database accounts
|Source DRDS instance||The read permissions on the objects that you want to synchronize.||Manage database accounts|
|Destination PolarDB for MySQL cluster||The read and write permissions on the objects in the destination cluster.||Create a database account|
- Go to the Data Synchronization page of the new DTS console.
- In the upper-left corner of the page, select the region where the data synchronization
- Click Create Task. On the page that appears, configure the source and destination databases.Warning After you select the source and destination instances, we recommend that you read the Limits displayed in the upper part of the page. This ensures that you create and run the data synchronization task.
Section Parameter Description N/A Task Name
The task name that DTS automatically generates. We recommend that you specify a descriptive name that makes it easy to identify the task. You do not need to use a unique task name.
Source Database Database Type Select PolarDB-X 1.0. Access Method Select Alibaba Cloud Instance. Instance Region Select the region in which the source DRDS instance resides. Instance ID Select the ID of the source DRDS instance. Database Account Enter the database account of the source DRDS instance. For information about the permissions that are required for the account, see Permissions required for database accounts. Database Password
The password of the database account.
Destination Database Database Type Select PolarDB for MySQL. Access Method Select Alibaba Cloud Instance. Instance Region Select the region in which the destination PolarDB for MySQL cluster resides. PolarDB Cluster ID Select the ID of the destination PolarDB for MySQL cluster. Database Account Enter the database account of the destination PolarDB for MySQL cluster. For information about the permissions that are required for the account, see Permissions required for database accounts. Database Password
The password of the database account.
- In the lower part of the page, click Test Connectivity and Proceed. 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 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 objects to migrate.
- Basic Settings
Parameter Description Task Stages
Incremental Data Synchronization is selected by default. You must also select Schema Synchronization and Full Data Synchronization. After the precheck is complete, DTS synchronizes the historical data of selected objects from the source instance to the destination cluster. The historical data is the basis for subsequent incremental synchronization.
Processing Mode of Conflicting Tables
Precheck and Report Errors: checks whether the destination database contains tables that have the same names as tables in the source database. If the source and destination databases do not contain identical table names, the precheck is passed. Otherwise, an error is returned during the precheck and the data synchronization task cannot be started.Note You can use the object name mapping feature to rename the tables that are migrated to the destination database. You can use this feature if the source and destination databases contain identical table names and the tables in the destination database cannot be deleted or renamed. For more information, see Map object names.
- Ignore Errors and Proceed: skips the precheck for identical table names in the source and destination databases.
Warning If you select Ignore Errors and Proceed, data inconsistency may occur and your business may be exposed to potential risks.
- If the source and destination databases have the same schema, and a data record has
the same primary key as an existing data record in the destination database:
- During full data synchronization, DTS does not synchronize the data record to the destination database. The existing data record in the destination database is retained.
- During incremental data synchronization, DTS synchronizes the data record to the destination database. The existing data record in the destination database is overwritten.
- If the source and destination databases have different schemas, initial data synchronization may fail. In this case, only part of the columns are synchronized, or the data synchronization task fails.
- If the source and destination databases have the same schema, and a data record has the same primary key as an existing data record in the destination database:
Select one or more objects from the Source Objects section and click the icon to add the objects to the Selected Objects section.Note You can select tables as objects to synchronize.
If you select an entire database as the object to synchronize, DTS does not synchronize the changes made to add and delete tables from the source database to the destination database.
Rename Databases and Tables
- To rename an object in the destination instance, right-click the object in the Selected Objects section. For more information, see Map the name of a single object.
- To rename multiple objects at a time in the destination instance, click Batch Edit in the upper-right corner of the Selected Objects section. For more information, see Map multiple object names at a time.
You can specify WHERE conditions to filter data. For more information, see Use SQL conditions to filter data.
Select the SQL operations to be synchronized In the Selected Objects section, right-click an object. In the dialog box that appears, select the SQL operations that you want to synchronize. For more information, see SQL operations that can be synchronized.
- Advanced Settings
Parameter Description Set AlertsSpecifies whether to set alerts for the data synchronization task. If you select yes, DTS sends notifications to contacts if the task fails or the synchronization latency exceeds the upper limit.
- No: does not set alerts.
- Yes: sets alerts. In this case, you must also set the alert threshold and alert contacts.
Capitalization of Object Names in Destination Instance
Specifies the capitalization of database names, table names, and column names in the destination instance. By default, DTS default policy is selected. You can select other options to make sure that the capitalization of object names is consistent with that of the source or destination database. For more information,see Specify the capitalization of object names in the destination instance.
Retry Time for Failed ConnectionSpecifies the retry time range for failed connections. Valid values: 10 to 1440. Unit: minutes. Default value: 120. We recommend that you set the retry time range to more than 30 minutes. If DTS reconnects to the source and destination databases within the specified time range, DTS resumes the data synchronization task. Otherwise, the data synchronization task fails.Note
- If an instance serves as the source or destination database of multiple data synchronization tasks, the less value that is specified for the instance takes precedence.
- When DTS retries a connection, you are charged for the DTS instance. We recommend that you specify the retry time range based on your business needs. You can also release the DTS instance at your earliest opportunity after the source and destination instances are released.
- Basic Settings
- Click Next: Save Task Settings and Precheck in the lower part of the page. 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 causes, you can run a precheck again.
- If you do not need to troubleshoot the issues, you can ignore failed items and run a precheck again.
- Wait until the Success Rate becomes 100%. Then, click Next: Purchase Instance.
- On the Purchase Instance page, specify the billing method and specifications for the data synchronization
instance. The following table describes related parameters.
Section Parameter Description Parameters Billing method
- Subscription: You pay for your subscription when you create an instance. The subscription billing method is more cost-effective than the pay-as-you-go billing method for long-term use.
- Pay-as-you-go: A pay-as-you-go instance is billed on an hourly basis. For short-term use, we recommend that you select the pay-as-you-go billing method. If you no longer need a pay-as-you-go instance, you can release the instance to reduce costs.
Instance Class DTS provides several instance classes that have different performance in synchronization speed. You can select an instance class based on your business scenario. For more information, see Specifications of data synchronization instances. Subscription Duration If you select the subscription billing method, set the subscription duration and the number of instances that you want to create. The subscription duration can be one to nine months or one to three years.Note This parameter is available only if you select the subscription billing method.
- Read and select Data Transmission Service (Pay-as-you-go) Service Terms.
- Click Buy and Start to start the data synchronization task. You can view the progress of the task in the task list.