Data Transmission Service:Migrate data from a Db2 for LUW database to an RDS for MySQL instance

Schema migration

• DTS migrates foreign keys from the source database to the destination database.

• During full and incremental data migration, DTS temporarily disables foreign key constraint checks and cascade operations at the session level. Performing cascade or delete operations on the source during migration may cause data inconsistency.

Source database

• The server to which the source database belongs must have sufficient outbound bandwidth. Otherwise, the data migration speed decreases.

• Tables must have PRIMARY KEY or UNIQUE constraints with all unique fields. Without these constraints, the destination database may contain duplicate records.

• When migrating individual tables, a single task supports a maximum of 1,000 tables. Exceeding this limit causes a request error. To migrate more than 1,000 tables, split the migration into multiple tasks or migrate the entire database instead.

• For incremental data migration, the data logging feature must be enabled on the source database. DTS returns an error during the precheck if it is not enabled.

• Log retention requirements: Insufficient log retention may cause the task to fail, or result in data inconsistency or data loss. After full data migration is complete, you can reduce the retention period to more than 24 hours. Failure to meet these requirements means the DTS service level agreement (SLA) does not guarantee reliability or performance.

  • Incremental migration only: retain logs for more than 24 hours.

  • Full and incremental migration combined: retain logs for at least 7 days.

• During full data migration, avoid DDL operations that change database or table schemas. Such changes cause the migration task to fail.

• During full-only migration, avoid writing data to the source database. To ensure data consistency, run full data migration and incremental data migration together.

Incremental data migration

DTS migrates incremental data using the Change Data Capture (CDC) replication technology of Db2 for LUW. This technology has its own limitations. See General data restrictions for SQL Replication.

SQL operations supported during incremental data migration:

Other limitations

• Migrate data during off-peak hours. Full data migration uses read and write resources on both the source and destination databases, which may increase server load.

• Concurrent INSERT operations during full data migration cause fragmentation in destination tables. After full data migration, the destination tablespace is larger than the source.

• Writing to the destination database using tools other than DTS during migration may cause data inconsistency. Use Data Management (DMS) for DDL operations after migration. See Perform lock-free DDL operations.

• If a DDL statement fails in the destination database, DTS continues running. View failed DDL statements in the task logs. See View task logs.

Self-managed Db2 for LUW

• A primary/secondary switchover on the source while a migration task is running causes the task to fail.

• DTS calculates migration latency by comparing the timestamp of the latest migrated data in the destination database against the current timestamp in the source. If no DML operations run on the source for an extended period, latency figures may be inaccurate. To refresh latency, run a DML operation on the source. If you are migrating an entire database, create a heartbeat table that is updated every second.

Step 1: Open Data Migration Tasks

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 layout and operations may vary. See Simple mode and Customize the layout and style of the DMS console for details. 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.

Step 3: Configure source and destination databases

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

Source database

Destination database

Step 4: Test connectivity

Click Test Connectivity and Proceed.

DTS automatically adds its CIDR blocks to the IP address whitelist of Alibaba Cloud database instances, or to the security group rules of ECS instances. For self-managed databases in a data center or hosted by a third-party cloud provider, manually add the DTS CIDR blocks to the database IP address whitelist. See Add the CIDR blocks of DTS servers to the security settings of on-premises databases.

If DTS hosts the source database on multiple ECS instances, add the DTS CIDR blocks to the security group rules of each ECS instance manually.

Step 5: Configure migration objects

Parameter	Description
Migration Types	Select the migration types based on your cutover strategy: <br>- Schema migration and full data migration only: select Schema Migration and Full Data Migration.<br>- Zero-downtime migration with service continuity: select Schema Migration, Full Data Migration, and Incremental Data Migration.<br><br> Note If you do not select Incremental Data Migration, avoid writing to the source database during migration to maintain data consistency.
Processing Mode of Conflicting Tables	- Precheck and Report Errors: checks for tables with identical names in source and destination. If identical names exist, the precheck fails and the task cannot start. Use the object name mapping feature to rename tables if needed. See Map object names.<br>- Ignore Errors and Proceed: skips the identical name check. Warning This may cause data inconsistency. If the schemas differ between source and destination, only specific columns are migrated or the task fails.
Capitalization of Object Names in Destination Instance	Controls capitalization of database names, table names, and column names in the destination. The default is DTS default policy. See Specify the capitalization of object names in the destination instance.
Source Objects	Select objects from the Source Objects section and click to move them to the Selected Objects section. You can select columns, tables, or databases. Selecting tables or columns excludes other objects such as views, triggers, and stored procedures.
Selected Objects	Right-click an object to rename it or set WHERE filter conditions. Click Batch Edit in the upper-right corner to rename multiple objects at once. See Map object names and Use SQL conditions to filter data. <br><br> Note Object name mapping may cause data inconsistency if dependent objects are not also migrated. For incremental migration of specific SQL operations on an object, right-click the object in Selected Objects and select the SQL operations to include.

Step 6: Configure advanced settings

Click Next: Advanced Settings.

Data verification

To configure data verification, see Enable data verification.

Advanced settings

Step 7: Save settings and run a precheck

Click Next: Save Task Settings and Precheck.

To preview the API parameters for configuring the DTS task, move the pointer over Next: Save Task Settings and Precheck and click Preview OpenAPI parameters before proceeding.

DTS runs a precheck before starting the migration task.

• If the precheck fails, click View Details next to the failed item, resolve the issue, and run the precheck again.

• If an alert appears for an item:

  • If the alert cannot be ignored, click View Details, resolve the issue, and run the precheck again.

  • If the alert can be ignored, click Confirm Alert Details, then click Ignore > OK > Precheck Again. Ignoring alerts may cause data inconsistency.

Step 8: Purchase the migration instance

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

On the Purchase Instance page, configure the following parameters.

Step 9: Start the migration

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

The migration task starts. Track progress in the task list.