Data Transmission Service:Migrate data from a MySQL-compatible OceanBase database to a PolarDB for MySQL cluster

Source database constraints

• The source database cannot be an ApsaraDB for OceanBase database.

• The source database server must have sufficient outbound bandwidth. Insufficient bandwidth reduces migration speed.

• Tables to be migrated must have PRIMARY KEY or UNIQUE constraints, and all fields must be unique. Otherwise, the destination database may contain duplicate records.

• If you select tables as the migration objects and need to rename tables or columns in the destination database, a single task can migrate up to 1,000 tables. Migrating more than 1,000 tables in a single task causes a request error. In this case, split the migration into multiple tasks or migrate the entire database instead.

• Data of the GEOMETRY type can only be migrated using full data migration. Incremental data migration is not supported for this type.

• Column names in a MySQL database are case-insensitive. If the source database has multiple columns whose names differ only in capitalization, DTS migrates data from these columns into the same destination column, which may produce unexpected results.

Other constraints

• DTS does not support converting data from the DATETIME type to the VARCHAR type.

• Throttling is not available for full data migration.

• If the source database name does not comply with PolarDB for MySQL naming conventions, create the destination database in the PolarDB for MySQL cluster before configuring the migration task. Then use the object name mapping feature to rename it in the Configure Objects and Advanced Settings step. For naming conventions and how to create a database, see Database Management.

• For columns of the FLOAT or DOUBLE type, DTS applies ROUND(COLUMN,PRECISION) to retrieve values. If no precision is specified, DTS defaults to 38 digits for FLOAT and 308 digits for DOUBLE. Verify that these defaults meet your business requirements.

• DTS automatically retries failed tasks for up to seven days. Before switching workloads to the destination database, stop or release any failed tasks, or run REVOKE to remove DTS write permissions on the destination database. Otherwise, a resumed task may overwrite destination data with source data.

• If a DDL statement fails to execute in the destination database, the DTS task continues running. View failed DDL statements in the task logs. For details, see View task logs.

Step 1: Go to the Data Migration Tasks page

1. Log on to the Data Management (DMS) console.

2. In the top navigation bar, click DTS.

3. In the left-side navigation pane, choose DTS (DTS) > Data Migration.

Navigation may vary based on the DMS console mode and layout. For details, see Simple mode and Customize the layout and style of the DMS console. You can also go directly to the Data Migration Tasks page in the new DTS console.

Step 2: Select the region

From the drop-down list next to Data Migration Tasks, select the region where the data migration instance resides.

In the new DTS console, select the region in the upper-left corner of the page.

Step 3: Configure source and destination databases

Click Create Task. On the Create Task wizard page, configure the following parameters.

Source database

If the source database is self-managed, set up the required environment before migration. For details, see Preparation overview.

Destination database

Step 4: Test connectivity

Click Test Connectivity and Proceed.

If the source database uses an IP address whitelist, add the CIDR blocks of DTS servers to the whitelist before clicking Test Connectivity and Proceed.

• Alibaba Cloud database instances (such as ApsaraDB RDS for MySQL or ApsaraDB for MongoDB): DTS adds its CIDR blocks automatically.

• Self-managed databases on ECS: DTS adds its CIDR blocks to the ECS security group rules automatically. Ensure that the ECS instance can access the database. If the database spans multiple ECS instances, add the CIDR blocks to each instance manually.

• Self-managed databases in a data center or on a third-party cloud: Add the CIDR blocks manually to the database IP address whitelist.

For the list of DTS server CIDR blocks, see Add the CIDR blocks of DTS servers.

Step 5: Configure objects and migration settings

Object name mapping may cause data inconsistency or break objects that depend on the renamed object. For example, non-full table migration with column mapping can result in data loss if source columns are absent in the destination schema.

Step 6: Configure advanced settings

Click Next: Advanced Settings and configure the following parameters.

During full data migration, DTS uses read and write resources on both the source and destination databases, which increases server load. Run migrations during off-peak hours. After full data migration completes, concurrent INSERT operations may cause table fragmentation in the destination database, so the destination tablespace will be larger than the source.

Step 7: Run the precheck

Click Next: Save Task Settings and Precheck.

To preview the API parameters for this task configuration before saving, hover over Next: Save Task Settings and Precheck and click Preview OpenAPI parameters.

DTS runs a precheck before starting the migration task. The task can only start after the precheck passes.

• If a precheck item fails, click View Details next to the failed item to see the cause, fix the issue, and run the precheck again.

• If a precheck item generates an alert, handle it based on the scenario:

  • If the alert cannot be ignored, click View Details next to the failed item, troubleshoot the issues, and run the precheck again.

  • If the alert can be safely ignored, click Confirm Alert Details, then click Ignore in the View Details dialog box, click OK, and click Precheck Again.

Step 8: Purchase the DTS instance

Wait until the success rate reaches 100%, then click Next: Purchase Instance.

On the Purchase Instance page, configure the following:

Step 9: Start the migration task

Read and select the Data Transmission Service (Pay-as-you-go) Service Terms check box, then click Buy and Start. Monitor task progress in the task list.