Synchronize Db2 for LUW to ApsaraDB RDS for MySQL - Data Transmission Service

You can use Data Transmission Service (DTS) to synchronize data from a Db2 for LUW database to an ApsaraDB RDS for MySQL instance.

Prerequisites

You have created a destination ApsaraDB RDS for MySQL instance. For more information, see Create an ApsaraDB RDS for MySQL instance.
If you need to perform full synchronization, the storage space of the destination database must be larger than the space occupied by the source database.

Limitations

Note

Limit type	Description
Limits on the source database	The server that hosts the source database must have sufficient outbound bandwidth. Otherwise, the data synchronization speed decreases. The tables to be synchronized must have PRIMARY KEY or UNIQUE constraints, and all fields must be unique. Otherwise, the destination database may contain duplicate data records. If you select tables as the objects to be synchronized and you want to modify the tables in the destination database, such as renaming tables or columns, you can synchronize up to 5,000 tables in a single task. If you synchronize more than 5,000 tables, a request error occurs. In this case, we recommend that you split the tables across multiple tasks or synchronize the entire database. The data logging feature must be enabled. Otherwise, error messages are returned during precheck, and the data synchronization task cannot be started. Note If you perform only incremental data synchronization, the data logs of the source database must be retained for more than 24 hours. If you perform both full and incremental data synchronization, the data logs must be retained for at least seven days. Otherwise, DTS may fail to obtain the data logs and the task may fail. In exceptional circumstances, data inconsistency or loss may occur. After full data synchronization is complete, you can set the retention period to more than 24 hours. Make sure that you set the retention period based on these requirements. Otherwise, the service reliability or performance stated in the SLA of DTS cannot be guaranteed. During schema synchronization and full data synchronization, do not perform DDL operations that change the database or table schema. Otherwise, the data synchronization instance fails.
Other limits	DTS synchronizes incremental data from a Db2 for LUW database to the destination database based on the CDC replication technology of Db2 for LUW. The CDC replication technology has its own limits. For more information, see General data restrictions for SQL Replication. Evaluate the impact of data synchronization on the performance of the source and destination databases before you start. We recommend that you synchronize data during off-peak hours. During initial full data synchronization, DTS uses read and write resources of the source and destination databases, which may increase the load on the database servers. During initial full data synchronization, concurrent INSERT operations cause fragmentation in the destination tables. After full data synchronization is complete, the used tablespace of the destination database is larger than that of the source database. 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 synchronize table schemas, set the `character_set_server` parameter at the instance level in the destination database to utf8mb4. During data synchronization, we recommend that you use only DTS to write data to the destination database to prevent data inconsistency. After data synchronization is complete, you can use DMS to execute DDL statements online. For more information, see Perform lock-free DDL operations. If DDL statements fail to be executed in the destination database, the data synchronization task continues to run. You can view the DDL statements that fail to be executed in the task logs. For more information about how to view the task logs, see View task logs. If you write columns with names that differ only in case to the same table in the destination MySQL database, unexpected results may occur because MySQL column names are case-insensitive. After data synchronization completes (the instance's Status is Completed), you should use the `ANALYZE TABLE <table_name>` command to confirm that all data is written to the target table. For example, after the HA failover mechanism is triggered in the target MySQL database, data might be written only to memory, which can cause data loss. 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.
Special cases	The source Db2 for LUW database is a self-managed database. When you synchronize data from the Db2 for LUW database, note the following items: If you perform a primary/secondary switchover on the source database while the data synchronization task is running, the task fails. DTS calculates synchronization latency based on the timestamp of the latest synchronized data record in the destination database and the current timestamp in the source database. If no DML operation is performed on the source database for a long time, the synchronization latency may be inaccurate. If the synchronization latency is too high, you can perform a DML operation on the source database to update the latency. Note If you select an entire database as the object to be synchronized, you can create a heartbeat table. The heartbeat table is updated or receives data every second.

Billing

Synchronization type	Fee
Full data synchronization	Free of charge
Incremental data synchronization	Charged. See Billing overview.

Supported synchronization topologies

One-to-one one-way synchronization
One-to-many one-way synchronization
Cascading one-way synchronization
Many-to-one one-way synchronization

For more information about the synchronization topologies and their considerations, see Data synchronization topologies.

Supported SQL operations

Operation type	SQL statement
DML	INSERT, UPDATE, DELETE

Preparations

Create accounts and grant permissions

Database	Required permissions	References
Db2 for LUW	DBADM permissions	Create a user
ApsaraDB RDS for MySQL	Read and write permissions on the synchronization objects in the destination database	Create an account and Modify account permissions

Enable the log archiving feature for the Db2 for LUW database. For more information, see logarchmeth1 - Primary log archive method configuration parameter and logarchmeth2 - Secondary log archive method configuration parameter.

Procedure

Go to the sync task list page of the destination region. You can use one of the following two 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 Synchronization.
3. In the upper-left corner of the page, select the region where the sync 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 and Customize the layout and style of the DMS interface.
1. Log on to Data Management (DMS).
2. In the top menu bar, choose Data + AI > Data Transmission (DTS) > Data Synchronization.
3. To the right of Data Synchronization Tasks, select the region where the sync instance is located.
Click Create Task to open the task configuration page.
Optional: In the upper-right corner of the page, click New Configuration Page.
Note
- If the button in the upper-right corner is Back to Previous Version, you can skip this step.
- The new and old configuration pages have different parameters. We recommend that you use the new configuration page.

Configure the source and destination databases.

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 have to be unique.
Source Database	Select Existing Connection	To use a database instance that is added to the system (newly created or saved), select the database instance from the drop-down list. The database information is automatically configured. Note In the DMS console, this configuration item is named Select a DMS database instance.. If you have not added the database instance to the system, or you do not need to use an instance that is already added, manually configure the following database information.
	Database Type	Select DB2 for LUW.
	Connection Type	Select a value based on the deployment location of the source database. This topic uses Self-managed Database on ECS as an example. Note If the source instance is a self-managed database, you must also complete the necessary preparations. For more information, see Preparations for connecting to a self-managed database.
	Instance Region	Select the region where the Db2 for LUW database is located.
	Replicate Data Across Alibaba Cloud Accounts	This example uses a database instance that belongs to the current Alibaba Cloud account. Select No.
	ECS Instance ID	Enter the ID of the ECS instance that hosts the Db2 for LUW database.
	Port	Enter the service port of the Db2 for LUW database. The default value is 50000.
	Database Name	Enter the name of the database in the source Db2 for LUW instance that contains the objects to be synchronized.
	Database Account	Enter the database account for the Db2 for LUW database. For permission requirements, see Create accounts and grant permissions.
	Database Password	Enter the password that corresponds to the database account.
Destination Database	Select Existing Connection	To use a database instance that is added to the system (newly created or saved), select the database instance from the drop-down list. The database information is automatically configured. Note In the DMS console, this configuration item is named Select a DMS database instance.. If you have not added the database instance to the system, or you do not need to use an instance that is already added, manually configure the following database information.
	Database Type	Select MySQL.
	Connection Type	Select Alibaba Cloud Instance.
	Instance Region	Select the region where the destination ApsaraDB RDS for MySQL instance is located.
	Replicate Data Across Alibaba Cloud Accounts	This example uses a database instance that belongs to the current Alibaba Cloud account. Select No.
	RDS Instance ID	Select the ID of the destination ApsaraDB RDS for MySQL instance.
	Database Account	Enter the database account for the destination ApsaraDB RDS for MySQL instance. For permission requirements, see Create accounts and grant permissions.
	Database Password	Enter the password that corresponds to the database account.
	Connection Method	Select Non-encrypted or SSL-encrypted as needed. If you select SSL-encrypted, you must enable SSL encryption for the RDS for MySQL instance in advance. For more information, see Use a cloud certificate to quickly enable SSL encryption.

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, click Test Connectivity.
Note
Ensure that the IP address CIDR blocks of DTS servers are added to the security settings of the source and destination databases to allow access from DTS servers. This can be done automatically or manually. For more information, see Add the IP address CIDR blocks of DTS servers to a whitelist.

Configure task objects.

On the Configure Objects page, configure the objects to synchronize.

Parameter	Description
Synchronization Types	The synchronization types. By default, Incremental Data Synchronization is selected. You must also select Schema Synchronization and Full Data Synchronization. After the precheck is complete, DTS synchronizes the historical data of the selected objects from the source database to the destination cluster. The historical data is the basis for subsequent incremental synchronization.
Processing Mode of Conflicting Tables	Precheck and Report Errors: DTS checks for tables with the same name in the destination database. If a conflict exists, DTS reports an error during the precheck and does not start the task. Note If it is not practical to delete or rename the conflicting table, you can map the table to a different name. For more information, see Map object names. Ignore Errors and Proceed: Skips the check for tables with the same name in the destination database. Warning If you select Ignore Errors and Proceed, data inconsistency may occur. For example: If the table schemas are consistent, destination records with the same primary or unique key as source records are overwritten. If the table schemas are inconsistent, the task may fail or only partially synchronize data. Proceed with caution.
Source Objects	In the Source Objects box, click an object to synchronize, and then click to move it to the Selected Objects box. Note You can select databases, tables, and columns as synchronization objects. If you select tables or columns, other objects such as views, triggers, and stored procedures are not synchronized to the destination database.
Selected Objects	To rename an object in the target instance, right-click the synchronization object in the Selected Objects box. For configuration instructions, see Map a single schema, table, or column name. To rename multiple objects in the target instance at once, click Selected Objects in the upper-right corner of the Batch Edit box. For configuration instructions, see Map schema, table, and column names in batches. Note To select the SQL operations to be synchronized 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. To set a WHERE clause to filter data, right-click the table in the Selected Objects box and set the filter condition in the dialog box. For instructions, see Set filter conditions.

Click Next: Advanced Settings to configure advanced parameters.

Parameter	Description
Dedicated Cluster for Task Scheduling	By default, DTS schedules tasks on a shared cluster, and you do not need to select a cluster. For more stable performance, you can purchase a dedicated cluster to run DTS sync tasks. For more information, see What is a DTS dedicated cluster?.
Retry Time for Failed Connections	After a sync 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 also specify a custom retry duration from 10 to 1,440 minutes. We recommend that you set the duration to 30 minutes or more. If DTS successfully reconnects to the database within the specified duration, the sync task automatically resumes. Otherwise, the task fails. Note If you have multiple DTS instances (for example, Instance A and Instance B) that share the same source or destination, and you set the network retry time to 30 minutes for Instance A and 60 minutes for Instance B, the shorter duration of 30 minutes is used for both. Because DTS charges for task runtime during the connection retry period, we recommend that you customize the retry duration 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 sync task starts, if other non-connectivity issues occur with the source or destination database (such as DDL or DML execution exceptions), DTS reports an error and immediately starts continuous retry operations. The default retry duration is 10 minutes. You can also customize the retry duration within the range of 1 to 1,440 minutes. We recommend that you set it to 10 minutes or more. If the relevant operations are successful within the set retry duration, the sync task automatically resumes. Otherwise, the task fails. Important The value for Retry Time for Other Issues must be less than that for Retry Time for Failed Connections.
Enable Throttling for Full Data Synchronization	During the full synchronization stage, DTS consumes read and write resources from the source and destination databases, which can increase the database load. To reduce the load on the source and destination databases, you can set a rate limit for the full synchronization task by configuring the Queries per second (QPS) to the source database, RPS of Full Data Migration, and Data migration speed for full migration (MB/s) parameters. Note This configuration item is available only when Synchronization Types is set to Full Data Synchronization. You can also adjust the full synchronization rate after the sync instance is running.
Enable Throttling for Incremental Data Synchronization	You can also set a rate limit for the incremental synchronization task. To relieve pressure on the destination database, set the RPS of Incremental Data Synchronization and Data synchronization speed for incremental synchronization (MB/s).
Environment Tag	You can select an environment tag to identify the instance. This is not required for this example.
Configure ETL	Choose whether to enable the extract, transform, and load (ETL) feature. For more information, see What is ETL? Valid values: Yes: Enables the ETL feature. Enter data processing statements in the code editor. For more information, see Configure ETL in a data migration or data synchronization task. No: Disables the ETL feature.
Monitoring and Alerting	Specify whether to configure alerts. If the synchronization fails or the latency exceeds the specified threshold, a notification is sent to an alert contact. No: No alerts are configured. Yes: Configure alerts by setting an alert threshold and specifying an alert notification. For more information, see Configure monitoring and alerting during task configuration.

Click Next: Data Validation to configure a data validation task.
If you want to use the data validation feature, see Configure data validation for configuration instructions.

Save the task and run a precheck.
- To view the API parameters for configuring this instance, hover over the Next: Save Task Settings and Precheck button and click Preview OpenAPI parameters in the bubble.
- If you have finished viewing the API parameters, click Next: Save Task Settings and Precheck at the bottom of the page.
Note
- Before the synchronization job starts, DTS runs a precheck. The job can start only after all precheck items pass.
- If the precheck fails, click View Details for the failed item. Fix the issue as prompted, and then run the precheck again.
- If the precheck returns a warning:
  If a check item fails and cannot be ignored, click View Details next to the item. Follow the instructions to fix the issue, and then run the precheck again.
  For check items that can be ignored, you can click Confirm Alert Details, Ignore, OK, and Precheck Again in sequence to skip the warning and rerun the precheck. If you choose to shield the warning item, 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 billing method and link specification for the data synchronization instance. The following table describes these parameters in detail.

Category	Parameter	Description
New Instance Class	Billing Method	Subscription: You pay when you create the instance. This is suitable for long-term needs and is more cost-effective than pay-as-you-go. The longer the subscription duration, the higher the discount. Pay-as-you-go: You are charged on an hourly basis. This is suitable for short-term needs. You can release the instance immediately after use to save costs.
	Resource Group Configuration	The resource group to which the instance belongs. The default is default resource group. For more information, see What is Resource Management?.
	Link Specification	DTS provides sync specifications with different performance levels. The sync link specification affects the synchronization rate. You can choose a specification based on your business scenario. For more information, see Data synchronization link specifications.
	Subscription Duration	In subscription mode, select the duration and quantity for the subscription instance. You can choose a monthly subscription from 1 to 9 months, or a yearly subscription of 1, 2, 3, or 5 years. Note This option is only available when the billing method is Subscription.

After you complete the configuration, read and select Data Transmission Service (Pay-as-you-go) Service Terms.
Click Buy and Start. In the OK dialog box, click OK.
You can view the task progress on the Data Synchronization page.