Migrate OceanBase (MySQL mode) to PolarDB for MySQL-Data Transmission Service(DTS)-阿里云帮助中心

Prerequisites

The source OceanBase database must be a DTS-supported version.
- If the source database is ApsaraDB for OceanBase, DTS supports only cluster instances, not tenant instances.
- If the source database is a self-hosted OceanBase database, DTS supports only Community Edition 4.X.
You have created a target PolarDB for MySQL cluster with a storage capacity greater than that of the source OceanBase database. For more information, see Custom purchase and Purchase a subscription cluster.

Usage notes

Note

DTS migrates foreign keys during schema migration.
During full and incremental data migration, DTS temporarily disables constraint checks and foreign key cascades at the session level. Cascade updates or deletes on the source database while the task runs may cause data inconsistency.

Type	Description
Limitations on the source database	If the source database is an ApsaraDB for OceanBase instance: Manually configure an IP whitelist to allow DTS to access the instance. For more information, see Configure whitelist groups and Add the IP addresses of DTS servers to the whitelist. For incremental migration, you must enable binlog for the source database and retain the local binlogs for at least three days. For more information, see Enable the binlog service and Manage binlog. If the source database is a self-managed OceanBase database: For incremental migration, you must install oblogproxy (an incremental log proxy service) on the server where the OceanBase database is deployed and configure the system tenant. For more information, see Install and deploy oblogproxy. Bandwidth requirements: The source database server must have sufficient outbound bandwidth. Insufficient bandwidth slows down the data migration. Tables to be migrated must have either a primary key or a unique constraint. Otherwise, duplicate data may occur in the destination database. When migrating specific tables and using features like object name mapping, a single data migration task is limited to 1,000 tables. Exceeding this limit causes the task to fail. To migrate more tables, split them into multiple tasks or configure a task to migrate the entire database. Limitations on operations on the source database: During schema migration and full data migration, do not perform any DDL operations. Otherwise, the data migration task fails. If you perform only full data migration, do not write new data to the source database. Otherwise, data inconsistency will occur between the source and destination databases. To ensure real-time data consistency, select schema migration, full data migration, and incremental data migration. The GEOMETRY data type is supported only for full data migration. DTS does not migrate data from hidden columns, which results in data loss.
Other limitations	DTS does not support converting data from the DATETIME type to the VARCHAR type. DTS does not currently support adjusting the full data migration speed. If the name of a database to be migrated does not comply with the naming conventions for PolarDB for MySQL, you must create a database in the destination PolarDB for MySQL cluster before you configure the data migration task. Then, you can use the object name mapping feature in the Configure Objects and Advanced Settings step. For more information about the database naming conventions for PolarDB for MySQL and how to create a database, see Manage databases. If your data includes four-byte characters—such as rare Chinese characters or emojis—the destination database and table must use the utf8mb4 charset. Note If you use DTS to migrate schemas, set the instance-level parameter `character_set_server` to utf8mb4 in the destination database. Before starting data migration, evaluate the performance of the source and destination databases. Perform data migration during off-peak hours. Otherwise, full data migration consumes I/O resources on both the source and destination databases, increasing the database load. During full data migration, concurrent INSERT operations cause table fragmentation in the destination database. Therefore, after full data migration is complete, the destination database's tablespace is larger than the source's. Confirm that the migration precision that DTS uses for FLOAT or DOUBLE columns meets your business requirements. DTS uses the `ROUND(COLUMN,PRECISION)` function to read values from these columns. If no precision is specified, the migration precision is 38 digits for FLOAT and 308 digits for DOUBLE. DTS attempts to resume a failed data migration task for up to seven days. Therefore, before switching your services to the destination instance, you must end or release the task. Alternatively, run the `revoke` command to revoke the write permissions of the DTS access account on the destination instance. This prevents an automatically resumed task from overwriting data in the destination instance. If the source database is an ApsaraDB for OceanBase instance and the DTS task includes incremental migration, DTS periodically attempts to run the CREATE DATABASE IF NOT EXISTS `test` statement on the source database to create a `test` database and write heartbeat data to advance the binlog position. If the account that DTS uses to access the source database does not have the required privileges to create databases, and no DML operations are performed on the source database for an extended period, the latency information may be inaccurate. Note If the displayed latency is too high, you can run a DML statement on the source database to update the latency information. If DTS fails to apply a DDL statement to the destination database, the data migration task continues to run. You must check the task logs for the failed DDL statement. For more information about how to view task logs, see View task logs. Because MySQL column names are case-insensitive, when migrating to a PolarDB for MySQL destination, DTS merges data from source columns whose names differ only in case (for example, 'Col' and 'col') into a single column. This can lead to unexpected results. If a task fails, DTS support staff will attempt to restore it within eight hours. During restoration, they may restart the task or adjust its parameters. Note Only DTS task parameters are modified—not database parameters. Parameters that may be adjusted include those listed in Modify instance parameters.

Billing

Migration type	Task configuration fee	Data transfer cost
Schema migration and full data migration	Free of charge.	No charge for this example.
Incremental data migration	Charged. For more information, see Billing overview.	No charge for this example.

Supported SQL operations for incremental migration

Operation type	SQL statement
DML	INSERT, UPDATE, DELETE
DDL	ALTER TABLE, ALTER VIEW CREATE FUNCTION, CREATE INDEX, CREATE PROCEDURE, CREATE TABLE, CREATE VIEW DROP INDEX, DROP TABLE RENAME TABLE Important A RENAME TABLE operation may cause data inconsistency. For example, if you select only one table as the migration object and rename the table in the source instance during migration, the data of this table is not migrated to the destination database. To prevent this issue, select the entire database to which the table belongs as the migration object when you configure the data migration task. Make sure that the databases to which the table belongs before and after the RENAME TABLE operation are both included in the migration objects. TRUNCATE TABLE

Database account permissions

Database			Schema migration	Full migration	Incremental migration
Source database	Self-managed OceanBase	User	SELECT permission
	Self-managed OceanBase	Tenant	Regular tenant	Regular tenant	Regular tenant Important For incremental data migration, install oblogproxy (an incremental log proxy service) on the OceanBase database server and configure a system tenant. For more information, see Install and deploy oblogproxy.
	ApsaraDB for OceanBase	Tenant	Regular tenant	Regular tenant	Regular tenant
	ApsaraDB for OceanBase	Database account	SELECT permission	SELECT permission	Read and write permissions
Destination database	PolarDB for MySQL		Read and write permissions

To create database accounts and grant permissions, see the following topics:

For self-managed OceanBase databases, see Create a tenant, Create a user, and Grant privileges.
For an ApsaraDB for OceanBase instance, see Create a tenant and Create an account.
For PolarDB for MySQL instances, see Create and manage a database account.

Procedure

Navigate to the migration task list page for the destination region using one of the following methods.
From the DTS console
1. Log on to the Data Transmission Service (DTS) console.
2. In the navigation pane on the left, click Data Migration.
3. In the upper-left corner of the page, select the region where the migration instance is located.
From the DMS console

Note
The actual operations may vary based on the mode and layout of the DMS console. For more information, see Simple mode console and Customize the layout and style of the DMS console.
1. Log on to the Data Management (DMS) console.
2. In the top menu bar, choose Data + AI > Data Transmission (DTS) > Data Migration.
3. To the right of Data Migration Tasks, select the region where the migration instance is located.
Click Create Task to navigate to the task configuration page.
Optional: In the upper-right corner of the page, click New Configuration Page.
Note
- If you are already on the new configuration page (the button in the upper-right corner is Back to Previous Version), you can skip this step.
- The parameters on the new and old configuration pages are different. We recommend that you use the new configuration page.

Configure the source and destination databases.

ApsaraDB for OceanBase for MySQL

Section	Parameter	Description
N/A	Task Name	DTS automatically generates a task name. We recommend that you specify a descriptive name for easy identification. The name does not need to be unique.
Source Database	Select Existing Connection	To use a database instance that has been added to the system (created or saved), select the desired database instance from the drop-down list. The database information below will be automatically configured. Note In the DMS console, this parameter is named Select a DMS database instance.. If you have not registered the database instance with the system, or do not need to use a registered instance, manually configure the database information below.
	Database Type	Select ApsaraDB OceanBase for MySQL.
	Access Method	Select Alibaba Cloud Instance.
	Instance Region	Select the region of the source ApsaraDB for OceanBase for MySQL instance.
	Replicate Data Across Alibaba Cloud Accounts	In this example, a database instance under the current Alibaba Cloud account is used. Select No.
	Instance ID	Select the instance ID of the source ApsaraDB for OceanBase for MySQL instance.
	Tenant ID	Select the tenant ID of the source ApsaraDB for OceanBase for MySQL instance. Note For information about how to view the tenant ID, see Tenant details.
	Database Account	Enter the database account for the source OceanBase database. For information about the required permissions, see Required database account permissions.
	Database Password	Enter the password for the specified database account.
Destination Database	Select Existing Connection	To use a database instance that has been added to the system (created or saved), select the desired database instance from the drop-down list. The database information below will be automatically configured. Note In the DMS console, this parameter is named Select a DMS database instance.. If you have not registered the database instance with the system, or do not need to use a registered instance, manually configure the database information below.
	Database Type	Select PolarDB for MySQL.
	Access Method	Select Alibaba Cloud Instance.
	Instance Region	Select the region of the destination PolarDB for MySQL cluster.
	PolarDB Cluster ID	Select the ID of the destination PolarDB for MySQL cluster.
	Database Account	Enter the database account for the destination PolarDB for MySQL cluster. For information about the required permissions, see Required database account permissions.
	Database Password	Enter the password for the database account.
	Encryption	Select a connection type as needed. For more information about the SSL encryption feature, see Enable SSL encryption.

Self-managed OceanBase

Section	Parameter	Description
N/A	Task Name	DTS automatically generates a task name. We recommend that you specify a descriptive name for easy identification. The name does not need to be unique.
Source Database	Select Existing Connection	To use a database instance that has been added to the system (created or saved), select the desired database instance from the drop-down list. The database information below will be automatically configured. Note In the DMS console, this parameter is named Select a DMS database instance.. If you have not registered the database instance with the system, or do not need to use a registered instance, manually configure the database information below.
	Database Type	Select ApsaraDB OceanBase for MySQL.
	Access Method	Select an option based on the deployment location of your self-managed OceanBase database. This example uses Public IP Address. Note Before connecting a self-managed database to DTS, complete the required preparations. For more information, see Overview of preparations. For information about common issues you may encounter when you configure the Source Database for a self-managed OceanBase database, see FAQ.
	Instance Region	Select the region where your self-managed OceanBase database is located.
	Domain Name or IP	Enter the endpoint of your self-managed OceanBase database.
	Port Number	Enter the connection port for your self-managed OceanBase database. The default value is 2881.
	IP Address in Log Proxy (Domain Name Not Supported)	Enter the IP address of the oblogproxy for your self-managed OceanBase database.
	Port in Log Proxy	Enter the listener port of the oblogproxy for your self-managed OceanBase database. The default value is 2983.
	Database Account	Enter the database account for your self-managed OceanBase database. For information about the required permissions, see Required database account permissions.
	Database Password	Enter the password for the specified database account.
Destination Database	Select Existing Connection	To use a database instance that has been added to the system (created or saved), select the desired database instance from the drop-down list. The database information below will be automatically configured. Note In the DMS console, this parameter is named Select a DMS database instance.. If you have not registered the database instance with the system, or do not need to use a registered instance, manually configure the database information below.
	Database Type	Select PolarDB for MySQL.
	Access Method	Select Alibaba Cloud Instance.
	Instance Region	Select the region of the destination PolarDB for MySQL cluster.
	PolarDB Cluster ID	Select the ID of the destination PolarDB for MySQL cluster.
	Database Account	Enter the database account for the destination PolarDB for MySQL cluster. For information about the required permissions, see Required database account permissions.
	Database Password	Enter the password for the database account.
	Encryption	Select a connection type as needed. For more information about the SSL encryption feature, see Enable SSL encryption.

FAQ

If the Log Proxy service is not installed for the OceanBase database, how do I specify the Log Proxy parameters?

Leave the IP Address in Log Proxy (Domain Name Not Supported) and Port in Log Proxy fields empty. Additionally, do not select Incremental Data Migration for Migration Types in the next step. Otherwise, the task will fail.
What if my database's region is not in the Instance Region drop-down list?

You can select the region that is geographically closest to your database.
If the OceanBase database is deployed in a cluster, what should I enter for Domain Name or IP?

Enter the IP address of the OBServer node that you specified when you configured the cluster.
How do I specify the Port Number of the OceanBase database?
- If the OceanBase database is deployed on a single node, you can keep the default value.
- If the OceanBase database is deployed in a cluster, you must enter the SQL port that you specified when you configured the cluster.
How do I specify the Database Account for the OceanBase database?

The Database Account must use the <username>@<tenant_name> format. For example, an account for user dtstest in the dts tenant should be entered as dtstest@dts.

After you complete the configuration, click Test Connectivity and Proceed at the bottom of the page. In the CIDR Blocks of DTS Servers dialog box that appears, click Test Connectivity.

Note
Ensure that the IP address segments of the DTS service are automatically or manually added to the security settings of the source and destination databases to allow access from DTS servers. For more information, see Add DTS server IP addresses to a whitelist.

Configure the task objects.

On the Configure Objects page, configure the objects that you want to migrate.

Parameter	Description
Migration Types	If you only need to perform a full migration, select both Schema Migration and Full Data Migration. To perform a migration with no downtime, select Schema Migration, Full Data Migration, and Incremental Data Migration. Note If you do not select Schema Migration, you must ensure that a database and tables to receive the data exist in the destination database. You can also use the object name mapping feature in the Selected Objects box as needed. If you do not select Incremental Data Migration, do not write new data to the source instance during data migration to ensure data consistency.
Processing Mode of Conflicting Tables	Precheck and Report Errors: Checks whether tables with the same names exist in the destination database. If no tables with the same names exist, the precheck is passed. If tables with the same names exist, an error is reported during the precheck, and the data migration task does not start. Note If a table in the destination database has the same name but cannot be easily deleted or renamed, you can change the name of the table in the destination database. For more information, see Object name mapping. Ignore Errors and Proceed: Skips the check for tables with the same names. Warning Selecting Ignore Errors and Proceed may cause data inconsistency and business risks. For example: If the table schemas are consistent and a record in the destination database has the same primary key value as a record in the source database: During full migration, DTS keeps the record in the destination database. The record from the source database is not migrated. During incremental migration, DTS does not keep the record in the destination database. The record from the source database overwrites the record in the destination database. If the table schemas are inconsistent, only some columns of data may be migrated, or the migration may fail. Proceed with caution.
Capitalization of Object Names in Destination Instance	You can configure the case sensitivity policy for the names of migrated objects, such as databases, tables, and columns, in the destination instance. By default, DTS default policy is selected. You can also choose to keep the case sensitivity consistent with the default policy of the source or destination database. For more information, see Case sensitivity of object names in the destination database.
Source Objects	In the Source Objects box, click the objects to migrate, and then click to move them to the Selected Objects box. Note The granularity for selecting migration objects is database, table, and column. If you select only tables or columns as migration objects, other objects such as views, triggers, and stored procedures are not migrated to the destination database.
Selected Objects	To change the name of a single migration object in the target instance, right-click the object in the Selected Objects box. For more information, see Map individual schema, table, and column names. To change the names of multiple migration objects in the target instance, click Selected Objects in the upper-right corner of the Batch Edit box. For more information, see Map multiple schema, table, and column names. Note Using the object name mapping feature can cause data inconsistencies or failures in migrating other dependent objects. For example, if you use column mapping for a partial table migration or if the table schemas are inconsistent, data in columns that exist in the source but not the destination is lost. To filter data by using a WHERE clause, right-click the table that you want to migrate in the Selected Objects box and specify the filter condition in the dialog box that appears. For more information, see Set filter conditions. To select SQL operations for incremental data migration at the database or table level, right-click the object in the Selected Objects box and select the desired SQL operations in the dialog box that appears.

Click Next: Advanced Settings to configure advanced parameters.

Parameter	Description
Dedicated Cluster for Task Scheduling	By default, DTS schedules tasks on a shared cluster. You do not need to select one. If you want more stable tasks, you can purchase a dedicated cluster to run DTS migration tasks.
Select the engine type of the destination database	Select the engine type of the destination database based on your requirements. InnoDB: The default storage engine. X-Engine: An online transaction processing (OLTP) database storage engine.
Retry Time for Failed Connections	After the migration task starts, if the connection to the source or destination database fails, DTS reports an error and immediately begins to retry the connection. The default retry duration is 720 minutes. You can customize the retry time to a value from 10 to 1440 minutes. We recommend that you set the duration to more than 30 minutes. If DTS reconnects to the source and destination databases within the specified duration, the migration task automatically resumes. Otherwise, the task fails. Note For multiple DTS instances that share the same source or destination, the network retry time is determined by the setting of the last created task. Because you are charged for the task during the connection retry period, we recommend that you customize the retry time based on your business needs, or release the DTS instance as soon as possible after the source and destination database instances are released.
Retry Time for Other Issues	After the migration task starts, if a non-connectivity issue, such as a DDL or DML execution exception, occurs in the source or destination database, DTS reports an error and immediately begins to retry the operation. The default retry duration is 10 minutes. You can customize the retry time to a value from 1 to 1440 minutes. We recommend that you set the duration to more than 10 minutes. If the related operations succeed within the specified retry duration, the migration task automatically resumes. Otherwise, the task fails. Important The value of Retry Time for Other Issues must be less than the value of Retry Time for Failed Connections.
Enable Throttling for Full Data Migration	During full migration, DTS consumes read and write resources on the source and destination databases, which may increase the database load. If required, you can enable throttling for the full migration task. You can set Queries per second (QPS) to the source database, RPS of Full Data Migration, and Data migration speed for full migration (MB/s) to reduce the load on the destination database. Note This configuration item is available only if you select Full Data Migration for Migration Types. You can also adjust the full migration speed after the migration instance is running.
Enable Throttling for Incremental Data Migration	If required, you can also choose to set speed limits for the incremental migration task. You can set RPS of Incremental Data Migration and Data migration speed for incremental migration (MB/s) to reduce the load on the destination database. Note This configuration item is available only if you select Incremental Data Migration for Migration Types. You can also adjust the incremental migration speed after the migration instance is running.
Environment Tag	You can select an environment tag to identify the instance based on your requirements. This example does not require an environment tag.
Configure ETL	Based on your business needs, select whether to configure the ETL feature to process data. Yes: Configures the ETL feature. You must also enter data processing statements in the text box. No: Does not configure the ETL feature.
Monitoring and Alerting	Select whether to set alerts and receive alert notifications based on your business needs. No: Does not set an alert. Yes: Configure alerts by setting an alert threshold and an alert contact. If a migration fails or the latency exceeds the threshold, the system sends an alert notification.

Save the task and run a precheck.
- To view the parameters for configuring this instance when you call the API operation, move the pointer over the Next: Save Task Settings and Precheck button and click Preview OpenAPI parameters in the bubble that appears.
- If you do not need to view or have finished viewing the API parameters, click Next: Save Task Settings and Precheck at the bottom of the page.
Note
- Before the migration task starts, DTS performs a precheck. The task starts only after it passes the precheck.
- If the precheck fails, click View Details next to the failed check item, fix the issue based on the prompt, and then run the precheck again.
- If a warning is reported during the precheck:
  
  For check items that cannot be ignored, click View Details next to the failed item, fix the issue based on the prompt, and then run the precheck again.
  
  For check items that can be ignored, you can click Confirm Alert Details, Ignore, OK, and Precheck Again to skip the alert item and run the precheck again. If you choose to ignore a warning, it may cause issues such as data inconsistency and pose risks to your business.

Purchase the instance.

When the Success Rate is 100%, click Next: Purchase Instance.

On the Purchase page, select the link specification for the data migration instance. For more information, see the following table.

Category	Parameter	Description
New Instance Class	Resource Group Settings	Select the resource group to which the instance belongs. The default value is default resource group. For more information, see What is Resource Management?
New Instance Class	Instance Class	DTS provides migration specifications with different performance levels. The link specification affects the migration speed. You can select a specification based on your business scenario. For more information, see Data migration link specifications.

After the configuration is complete, read and select Data Transmission Service (Pay-as-you-go) Service Terms.
Click Buy and Start. In the OK dialog box that appears, click OK.

You can view the progress of the migration task on the Data Migration Tasks list page.
Note
- If the migration task does not include incremental migration, it stops automatically after the full migration is complete. After the task stops, its Status changes to Completed.
- If the migration task includes incremental migration, it does not stop automatically. The incremental migration task continues to run. While the incremental migration task is running, the Status of the task is Running.