Synchronize a Data Management (DMS) logical database to AnalyticDB for MySQL 3.0 - Data Transmission Service

Data Transmission Service (DTS) allows you to synchronize a logical database configured in Data Management (DMS) to AnalyticDB for MySQL 3.0. This helps you quickly build internal business intelligence (BI), interactive query, and real-time reporting systems.

Prerequisites

You have configured a logical database in DMS. The logical database must be created from sharded databases across multiple PolarDB for MySQL instances. For more information, see Logical database.
All PolarDB for MySQL instances that host the physical sharded databases for the DMS logical database must reside in the same region. They must also share a unified database account and password with read permissions on the physical sharded databases. For information about how to create and authorize an account, see Create and manage a database account.
You have created a destination AnalyticDB for MySQL 3.0 cluster. For more information, see Create a cluster.
The storage capacity of the AnalyticDB for MySQL 3.0 cluster must be larger than the storage used by the DMS logical database.

Limitations

Note

During schema synchronization, DTS does not synchronize foreign keys from the source database to the destination database.
During full and incremental data synchronization, DTS temporarily disables constraint checks and foreign key cascade operations at the session level. If you perform cascade update or delete operations on the source database while the task is running, data inconsistency may occur.
During schema synchronization, DTS does not support synchronizing materialized views to the target AnalyticDB for MySQL instance. If you need to use materialized views, manually create them in the target instance after the synchronization is complete.

Type	Description
Source database limitations	The tables to be synchronized must have a primary key or a unique constraint to ensure that each row is unique. Otherwise, duplicate data may appear in the destination database. If you synchronize at the table level and need to edit objects (for example, map table or column names), a single data synchronization task supports synchronizing up to 1,000 tables. If you exceed this limit, the task submission fails. In this case, split the tables into multiple tasks, or configure a database-level synchronization task. Binary log: Binary logging must be enabled, and `loose_polar_log_bin` must be set to on. Otherwise, the precheck fails and the data synchronization task cannot start. For an incremental data synchronization task, DTS requires that the local binary logs of the source database be retained for more than 24 hours. For a task that involves both full and incremental data synchronization, DTS requires that the local binary logs be retained for at least 7 days. You can change the retention period to more than 24 hours after the full data synchronization is complete. Otherwise, the task may fail because DTS cannot obtain the binary logs. In extreme cases, data may become inconsistent or be lost. Issues caused by a binary log retention period shorter than required are not covered by the DTS Service Level Agreement (SLA). During synchronization, do not perform DDL operations that add comments (for example, `ALTER TABLE table_name COMMENT='table_comment';`). Otherwise, the data synchronization task fails. Do not run DDL operations that change database or table schemas during schema synchronization or full synchronization. Otherwise, the synchronization task fails. Note During full synchronization, DTS queries the source database. This creates metadata locks that may block DDL operations on the source database.
Other limitations	You can configure synchronization from a DMS logical database to AnalyticDB for MySQL 3.0 only in the China (Shanghai) and Singapore regions. The destination database must contain a custom primary key. Or, in the Configurations for Databases, Tables, and Columns step, configure a Primary Key Column. Otherwise, synchronization may fail. Prefix indexes are not supported. If the source database contains prefix indexes, the data synchronization may fail. Due to the limitations of AnalyticDB for MySQL, when the disk space usage of a node in an AnalyticDB for MySQL cluster exceeds 80%, the write performance to the destination database degrades, causing DTS task latency. When usage exceeds 90%, data cannot be written to the destination database, causing the DTS task to fail. Estimate the required space based on the objects to be synchronized and ensure the destination cluster has sufficient storage space. If the destination AnalyticDB for MySQL 3.0 cluster is backing up while the DTS task runs, the task fails. Before starting data synchronization, evaluate the performance of the source and destination databases. We recommend performing data migration during off-peak hours. Otherwise, the initial full data synchronization consumes read and write resources on the source and destination databases, which can increase their load. Full data synchronization performs concurrent INSERT operations, which fragments tables in the destination database. As a result, the tablespace in the destination instance is larger than that in the source instance after full initialization is complete. For table-level data synchronization, do not use tools like `pt-online-schema-change` to perform online DDL changes on the synchronization objects in the source database. This causes the synchronization to fail. For table-level data synchronization, if DTS is the only source writing data to the destination database, you can use Data Management (DMS) to perform online DDL changes. For more information, see Perform lock-free DDL operations. During DTS synchronization, do not write data from other sources to the destination database. This can cause data inconsistency between the source and destination databases. For example, if data from another source is being written to the destination database while you use DMS to perform an online DDL change, data loss may occur in the destination database. 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. When AnalyticDB for MySQL is the destination, DTS supports writing only its supported data types, including basic data types and complex data types such as ARRAY, MAP, and JSON. DTS does not support writing other types such as MULTIVALUE.

Billing

Synchronization type	Pricing
Schema synchronization and full data synchronization	Free of charge.
Incremental data synchronization	Charged. For more information, see Billing overview.

Supported synchronization topologies

One-way one-to-one synchronization
One-way one-to-many synchronization
One-way many-to-one synchronization

For more information about various synchronization topologies and their limitations, see Synchronization topologies.

Supported SQL operations

Operation type	SQL statements
DML	INSERT, UPDATE, DELETE Note When data is written to the AnalyticDB for MySQL cluster, the UPDATE statement is automatically converted to the REPLACE INTO statement.

Procedure

Go to the data synchronization task list page in the destination region. You can do this in one of two ways.
DTS console
1. Log on to the 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 synchronization instance is located.
DMS console
Note
The actual steps may vary depending on the mode and layout of the DMS console. For more information, see Simple mode console and Customize DMS console layout and style.
1. Log on to the DMS console.
2. In the top menu bar, choose Data + AI > DTS (DTS) > Data Synchronization.
3. To the right of Data Synchronization Tasks, select the region of the synchronization instance.
Click Create Task to open the task configuration page.

Configure the source and destination databases.

Warning

After you select the source and destination instances, review the Limits at the top of the page. Otherwise, the task may fail or data inconsistency may occur.

Category	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	Database Type	Select DMS LogicDB.
	Connection Type	Select Alibaba Cloud Instance.
	Instance Region	Select the region where the DMS logical database resides.
	Database Account	Enter the unified database account for all PolarDB for MySQL instances that host the physical sharded databases for the DMS logical database. The account must have read permissions on the physical sharded databases. For more information, see Create and manage a database account.
	Database Password	Enter the password for the specified database account.
Destination Database	Database Type	Select AnalyticDB 3.0.
	Connection Type	Select Alibaba Cloud Instance.
	Instance Region	Select the region where the destination AnalyticDB for MySQL 3.0 cluster resides.
	Instance ID	Select the ID of the destination AnalyticDB for MySQL 3.0 cluster.
	Database Account	Enter the database account for the destination AnalyticDB for MySQL 3.0 cluster. The account must have read and write permissions.
	Database Password	Enter the password for the specified database account.

After you complete the configuration, click Test Connectivity and Proceed at the bottom of the page.
Note
Ensure that the IP address blocks of the DTS service are added to the security settings of the source and destination databases, either automatically or manually, to allow access from DTS servers. For more information, see Add the IP address whitelist of DTS servers.

Configure the task objects.

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

Parameter	Description
Synchronization Types	DTS always selects Incremental Data Synchronization. By default, you must also select Schema Synchronization and Full Data Synchronization. After the precheck, DTS initializes the destination cluster with the full data of the selected source objects, which serves as the baseline for subsequent incremental synchronization. Note If Full Data Synchronization is selected, you can synchronize the schema and data of the table that is created by executing the CREATE TABLE statement to the destination database.
Processing Mode of Conflicting Tables	Precheck and Report Errors: Checks for tables with the same names in the destination database. If any tables with the same names are found, an error is reported during the precheck and the data synchronization task does not start. Otherwise, the precheck is successful. Note If you cannot delete or rename the table with the same name in the destination database, you can map it to a different name in the destination. For more information, see Object name mapping. Ignore Errors and Proceed: Skips the check for tables with the same name in the destination database. Warning Selecting Ignore Errors and Proceed may cause data inconsistency and put your business at risk. For example: If the table schemas are consistent and a record in the destination database has the same primary key or unique key value as a record in the source database: During full data synchronization, DTS retains the destination record and skips the source record. During incremental synchronization, DTS overwrites the destination record with the source record. If the table schemas are inconsistent, data initialization may fail. This can result in only partial data synchronization or a complete synchronization failure. Use with caution.
Source Objects	In the Source Objects box, click the objects, and then click to move them to the Selected Objects box. Note You can select columns, tables, or databases as the objects to synchronize. If you select tables or columns, DTS does not synchronize other objects such as views, triggers, or stored procedures to the destination database. If you select a database as the object to synchronize, DTS applies the following default rules: If the source table has a primary key (single-column or composite), the primary key columns are used as the distribution keys. If the source table does not have a primary key, an auto-increment primary key column is generated in the destination table. This may cause data inconsistency between the source and destination databases.
Selected Objects	To rename a single object in the destination instance, right-click the object in the Selected Objects box. For more information, see Map a single object name. To rename multiple objects in bulk, click Batch Edit in the upper-right corner of the Selected Objects box. For more information, see Map multiple object names in bulk. Note To select the SQL operations to synchronize at the database or table level, right-click the object in the Selected Objects pane and choose the desired SQL operations from the dialog box that appears. To filter data by using a WHERE clause, right-click the table in the Selected Objects pane and specify the filter condition in the dialog box that appears. For instructions, see Specify filter conditions.

Click Next: Advanced Settings.

Parameter	Description
Dedicated Cluster for Task Scheduling	By default, DTS uses a shared cluster for tasks, so you do not need to make a selection. For greater task stability, you can purchase a dedicated cluster to run the DTS synchronization task. For more information, see What is a DTS dedicated cluster?.
Retry Time for Failed Connections	If the connection to the source or destination database fails after the synchronization task starts, 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 1,440 minutes. We recommend a duration of 30 minutes or more. If the connection is restored within this period, the task resumes automatically. Otherwise, the task fails. Note If multiple DTS instances (e.g., Instance A and B) share a source or destination, DTS uses the shortest configured retry duration (e.g., 30 minutes for A, 60 for B, so 30 minutes is used) for all instances. DTS charges for task runtime during connection retries. Set a custom duration based on your business needs, or release the DTS instance promptly after you release the source/destination instances.
Retry Time for Other Issues	If a non-connection issue (e.g., a DDL or DML execution error) occurs, DTS reports an error and immediately retries the operation. The default retry duration is 10 minutes. You can also customize the retry time to a value from 1 to 1,440 minutes. We recommend a duration of 10 minutes or more. If the related operations succeed within the set retry time, the synchronization task automatically resumes. Otherwise, the task fails. Important The value of Retry Time for Other Issues must be less than that of Retry Time for Failed Connections.
Enable Throttling for Full Data Synchronization	During full data synchronization, DTS consumes read and write resources from the source and destination databases, which can increase their load. To mitigate pressure on the destination database, you can limit the migration rate by setting Queries per second (QPS) to the source database, RPS of Full Data Migration, and Data migration speed for full migration (MB/s). Note This parameter is available only if Synchronization Types is set to Full Data Synchronization. You can also adjust the rate of full data synchronization when the synchronization instance is running.
Enable Throttling for Incremental Data Synchronization	You can also limit the incremental synchronization rate to reduce pressure on the destination database by setting 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 based on your needs. 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	Choose whether to set up alerts. If the synchronization fails or the latency exceeds the specified threshold, DTS sends a notification to the alert contacts. No: No alerts are configured. Yes: Configures alerts. You must also set the alert threshold and alert notifications. For more information, see Configure monitoring and alerting during task configuration.

Optional: After you complete the configuration, click Next: Configure Database and Table Fields to set the Type, Primary Key Column, Distribution Key, and partition key information (Partition Key, Partitioning Rules, and Partition Lifecycle) for the tables to sync in the destination database.
Note
- This step is available only if you select the Schema Synchronization checkbox for Synchronization Types during task object configuration. You can set Definition Status to All to make modifications.
- You can use the Primary Key Column to specify a composite primary key that consists of multiple columns. You must then select one or more columns from the Primary Key Column to serve as the Distribution Key and Partition Key. For more information, see CREATE TABLE.

Save the task and perform a precheck.
- To view the parameters for configuring this instance via an API operation, hover over the Next: Save Task Settings and Precheck button and click Preview OpenAPI parameters in the tooltip.
- If you have finished viewing the API parameters, click Next: Save Task Settings and Precheck at the bottom of the page.
Note
- Before a synchronization task starts, DTS performs a precheck. You can start the task only if the precheck passes.
- If the precheck fails, click View Details next to the failed item, fix the issue as prompted, and then rerun the precheck.
- If the precheck generates warnings:
  For non-ignorable warning, click View Details next to the item, fix the issue as prompted, and run the precheck again.
  For ignorable warnings, you can bypass them by clicking Confirm Alert Details, then Ignore, and then OK. Finally, click Precheck Again to skip the warning and run the precheck again. Ignoring precheck warnings may lead to data inconsistencies and other business risks. Proceed with caution.

Purchase the instance.

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

On the Purchase page, select the billing method and link specifications for the data synchronization instance. For more information, see the following table.

Category	Parameter	Description
New Instance Class	Billing Method	Subscription: You pay upfront for a specific duration. This is cost-effective for long-term, continuous tasks. Pay-as-you-go: You are billed hourly for actual usage. This is ideal for short-term or test tasks, as you can release the instance at any time to save costs.
	Resource Group Settings	The resource group to which the instance belongs. The default is default resource group. For more information, see What is resource management?.
	Instance Class	DTS offers synchronization specifications at different performance levels that affect the synchronization rate. Select a specification based on your business requirements. For more information, see Data synchronization link specifications.
	Subscription Duration	In subscription mode, select the duration and quantity of the instance. Monthly options range from 1 to 9 months. Yearly options include 1, 2, 3, or 5 years. Note This option appears only when the billing method is Subscription.

Read and select the checkbox for Data Transmission Service (Pay-as-you-go) Service Terms.
Click Buy and Start, and then click OK in the OK dialog box.
You can monitor the task progress on the data synchronization page.