Data Transmission Service:Migrate data from a PolarDB-X 1.0 instance to a DataHub project

Source database

• Table limit: If you select tables as migration objects and rename destination tables or columns, a single task supports up to 1,000 tables. Exceeding this limit causes a request error. Split the migration into multiple tasks, or migrate the entire database as a single object.

• Read-only instances: You cannot migrate data from a read-only PolarDB-X 1.0 instance.

• Binary log retention: Retain binary logs for more than 24 hours. If DTS cannot read the binary logs, the task fails and data loss or inconsistency may occur. Make sure that you set the retention period of binary logs based on the preceding requirements. Otherwise, the Service Level Agreement (SLA) of DTS does not guarantee service reliability or performance.

• Prohibited operations during migration: Do not upgrade or downgrade the source instance, migrate frequently-updated tables, change shard keys, or run DDL operations on source objects. These operations cause the migration task to fail.

• Foreign key constraints: During combined schema migration and incremental data migration, DTS disables constraint checks and cascade operations on foreign keys at the session level. If you run cascade delete operations on the source database during this period, data inconsistency may occur.

• Network type changes: If you change the network type of the PolarDB-X 1.0 instance during migration, update the network connection settings of the migration task accordingly.

• Write operations during schema-only migration: If you run schema migration without incremental data migration, stop writing to the source database during migration to prevent data inconsistency.

Other limitations

• Schedule migration during off-peak hours to reduce impact on source and destination database performance.

• 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, the failed task may resume and overwrite destination data with source data.

Usage notes

DTS periodically updates the dts_health_check.ha_health_check table in the source database to advance the binary log position.

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.

Console operations may vary based on the DMS console mode and layout. See Simple mode and Customize the layout and style of the DMS console. Alternatively, go directly to the Data Migration Tasks page in the new DTS console.

Step 2: Select a region

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

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

Step 3: Configure source and destination databases

Click Create Task, then configure the source and destination databases.

Source database settings

Destination Database

Step 4: Test connectivity

Click Test Connectivity and Proceed.

DTS also automatically adds its server CIDR blocks to the IP address whitelist of Alibaba Cloud database instances or Elastic Compute Service (ECS) security groups.

Step 5: Configure migration objects

Parameter	Description
Migration Types	Select Schema Migration, Incremental Data Migration, or both.
Processing Mode of Conflicting Tables	Precheck and Report Errors: fails the precheck if destination tables have the same names as source tables. Use object name mapping to rename conflicting tables before migration. Ignore Errors and Proceed: skips the name conflict check. If schemas match, DTS skips records with duplicate primary keys. If schemas differ, only specific columns are migrated or the task fails. Use with caution.
Naming Rules of Additional Columns	DTS adds extra columns to destination tables after migration. If those column names conflict with existing column names in the destination, migration fails. Select New Rule or Previous Rule to control naming. Check for conflicts before selecting. See Naming rules for additional columns.
Capitalization of Object Names in Destination Instance	Controls the case of database, table, and column names in the destination. The default uses the DTS policy. See Specify the capitalization of object names in the destination instance.
Source Objects	Select one or more objects, then click to move them to Selected Objects. Select tables or entire databases. If you select tables, DTS does not migrate views, triggers, or stored procedures.
Selected Objects	Right-click an object to rename it, add SQL filter conditions, or select specific SQL operations to migrate. To rename multiple objects at once, click Batch Edit. See Map object names and Use SQL conditions to filter data.

If a database is selected as a migration object and the source table has a primary key (single-column or composite), that primary key is used as the distribution key in the destination. If the source table has no primary key, DTS generates an auto-increment primary key column in the destination, which may cause data inconsistency.

Renaming an object with object name mapping may cause dependent objects to fail migration.

Step 6: Configure advanced settings

Click Next: Advanced Settings, then configure the following parameters.

DTS charges for retry attempts. Release the DTS instance promptly after the source and destination instances are released.

Step 7: Run the precheck

Click Next: Save Task Settings and Precheck.

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

DTS validates the task configuration before starting migration. The precheck covers connectivity, account permissions, binary log settings, and object compatibility.

• If a precheck item fails, click View Details to see the error, fix the issue, then click Precheck Again.

• If a precheck item triggers an alert that can be safely ignored, click Confirm Alert Details, then Ignore in the View Details dialog, click OK, and click Precheck Again.

Step 8: Purchase the migration instance

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

On the Purchase Instance page, configure the instance class.

Step 9: Start migration

Select the Data Transmission Service (Pay-as-you-go) Service Terms check box, then click Buy and Start.

The migration task starts and appears in the task list. Monitor the task progress from there.