This topic describes how to synchronize data from an ApsaraDB RDS for SQL Server instance to an AnalyticDB for MySQL V3.0 cluster by using Data Transmission Service (DTS).The data migration feature allows you to transfer and analyze data with ease.

Supported source databases

You can use DTS to synchronize data from the following types of SQL Server databases to an AnalyticDB for MySQL V3.0 cluster. In this topic, an ApsaraDB RDS for SQL Server instance is used to describe how to configure a data synchronization task. You can also follow the procedure to configure data synchronization tasks for other types of SQL Server databases.
  • ApsaraDB RDS for SQL Server instances
  • Self-managed databases that are hosted on Elastic Compute Service (ECS)

Prerequisites

  • The source ApsaraDB RDS for SQL Server instance is created. For more information, see Overview of data synchronization scenarios and Create an ApsaraDB RDS for SQL Server instance.
    Notice The version number of the ApsaraDB RDS for SQL Server instance can be 2012, 2014, 2016, 2017, or 2019.
  • The destination AnalyticDB for MySQL V3.0 cluster is created. For more information, see Create a cluster.
  • The available storage space of the destination AnalyticDB for MySQL V3.0 cluster is larger than the total size of the data in the source ApsaraDB RDS for SQL Server instance.

Limits

Note By default, DTS disables FOREIGN KEY constraints for the destination database in a data synchronization task. Therefore, the cascade and delete operations of the source database are not synchronized to the destination database.
Category Description
Limits on the source database
  • The tables to synchronize 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 synchronize and you want to edit tables (such as renaming tables or columns), up to 1,000 tables can be synchronized in a single data synchronization task. If you run a task to synchronize more than 1,000 tables, a request error occurs. In this case, we recommend that you split the tables, configure multiple tasks to synchronize the tables, or configure a task to synchronize the entire database.
  • A single data synchronization task can synchronize up to 10 databases. If you want to synchronize more than 10 databases, we recommend that you split the tables to synchronize or configure multiple tasks to synchronize the databases. Otherwise, the performance and stability of your data synchronization task may be compromised.
  • The following requirements for data logs must be met:
    • The data logging feature must be enabled. The backup mode must be set to Full, and full logical backup must be performed.
    • If you perform only incremental data synchronization, the data logs of the source database must be stored for more than 24 hours. If you perform both full data synchronization and incremental data synchronization, the data logs of the source database must be stored for at least seven days. After the full data synchronization is complete, you can set the retention period to more than 24 hours. Otherwise, DTS may fail to obtain the data logs and the task may fail. In exceptional circumstances, data inconsistency or loss may occur. Make sure that you set the retention period of data logs in accordance with the preceding requirements. Otherwise, the Service Level Agreement (SLA) of DTS does not ensure service reliability and performance.

Other limits
  • Requirements for the objects to synchronize:
    • DTS supports initial schema synchronization for the following types of objects: schema, table, view, function, and procedure.
      Warning ApsaraDB RDS for SQL Server and AnalyticDB for PostgreSQL are heterogeneous databases. The data types that they support do not have one-to-one correspondence. We recommend that you evaluate the impact of data type conversion on your business. For more information, see Data type mappings for schema synchronization.
    • DTS does not synchronize the schemas of assemblies, service brokers, full-text indexes, full-text catalogs, distributed schemas, distributed functions, CLR stored procedures, CLR scalar-valued functions, CLR table-valued functions, internal tables, systems, or aggregate functions.
    • DTS does not synchronize data of the following types: TIMESTAMP, CURSOR, ROWVERSION, HIERACHYID, SQL_VARIANT, SPATIAL GEOMETRY, SPATIAL GEOGRAPHY, and TABLE.
    • DTS does not synchronize tables that contain computed columns.
  • If you set SQL Server Incremental Synchronization Mode to Incremental Synchronization Based on Logs of Source Database in the Configure Objects and Advanced Settings step, the tables to synchronize must have clustered indexes that contain primary key columns. In addition, the table to synchronize cannot be compressed tables and cannot contain computed columns. Ignore the preceding limits in the mixed log-based parsing mode.
  • In the Incremental Synchronization Based on Logs of Source Database mode, DTS adds a heartbeat table named dts_log_heart_beat to the source database to ensure that the latency of data synchronization is accurate. In the mixed log-based parsing incremental synchronization mode, DTS creates a trigger named dts_cdc_sync_ddl, a heartbeat table named dts_sync_progress, and a storage table named dts_cdc_ddl_history by using DDL and enables Change Data Capture (CDC) for the database and some tables.
  • Due to the limits of AnalyticDB for MySQL , if the disk space usage of the nodes in an AnalyticDB for MySQL cluster reaches 80%, the performance of data writing to the destination database is compromised and the DTS task is delayed. If the usage reaches 90%, data cannot be written to the destination database and error messages are returned. We recommend that you estimate the required disk space based on the objects that you want to synchronize. You must ensure that the destination cluster has sufficient storage space.
  • Before you synchronize data, evaluate the impact of data synchronization on the performance of the source and destination databases. We recommend that you synchronize data during off-peak hours. During full data synchronization, DTS uses read and write resources of the source and destination databases. This may increase the loads of the database servers.
  • During full data synchronization, concurrent INSERT operations cause fragmentation in the tables of the destination database. Therefore, after the full data synchronization is complete, the tablespace of the destination database is larger than that of the source database.
  • We recommend that you do not use gh-ost or pt-online-schema-change to perform DDL operations on source tables during data synchronization. Otherwise, data synchronization may fail.
  • During data synchronization, we recommend that you use only DTS to write data to the destination database. This prevents data inconsistency between the source and destination databases. If you use tools other than DTS to write data to the destination database, data loss may occur in the destination database when you use DMS to perform online DDL operations.

Billing

Synchronization type Task configuration fee
Schema synchronization and full data synchronization Free of charge.
Incremental data synchronization Charged. For more information, see Pricing.

Supported synchronization topologies

  • One-way one-to-one synchronization
  • One-way one-to-many synchronization
  • One-way cascade synchronization
  • One-way many-to-one synchronization
For more information about synchronization topologies, see Synchronization topologies.

SQL operations that can be synchronized

Operation type SQL statement
DML INSERT, UPDATE, and DELETE
DDL
  • CREATE TABLE
    Note If a CREATE TABLE statement contains partitioning clauses, subpartitioning clauses, or functions, DTS does not synchronize the operation.
  • ADD COLUMN and DROP COLUMN
  • DROP TABLE
  • CREATE INDEX and DROP INDEX

Procedure

  1. Go to the Data Synchronization page of the new DTS console.
    Note You can also log on to the Data Management console. In the top navigation bar, click DTS. Then, in the left-side navigation pane, choose DTS (DTS) > Data Synchronization.
  2. In the upper-left corner of the page, select the region where the data synchronization instance resides.
    Region
  3. Click Create Task. On the page that appears, configure the source and destination databases.
    Warning After you select the source and destination instances, we recommend that you read the Limits displayed in the upper part of the page. This ensures that you create and run the data synchronization task.
    Configure the source and destination databases
    Section Parameter Description
    N/A Task Name

    The task name that DTS automatically generates. We recommend that you specify a descriptive name that makes it easy to identify the task. You do not need to use a unique task name.

    Source Database Database Type Select SQL Server.
    Access Method Select Cloud Instance.
    Instance Region The region where the source ApsaraDB RDS for SQL Server instance resides.
    Instance ID The ID of the source ApsaraDB RDS for SQL Server instance.
    Database Account The database account of the source ApsaraDB RDS for SQL Server instance. The account must have the owner permissions on the objects to synchronize. A privileged account has the required permissions.
    Database Password

    The password of the database account.

    Destination Database Database Type Select AnalyticDB for MySQL 3.0.
    Access Method Select Cloud Instance.
    Instance Region The region where the destination AnalyticDB for MySQL V3.0 cluster resides.
    Instance ID The ID of the destination AnalyticDB for MySQL V3.0 cluster.
    Database Account The database account of the destination AnalyticDB for MySQL V3.0 cluster. The account must have read and write permissions on the destination database.
    Database Password

    The password of the database account.

  4. In the lower part of the page, click Test Connectivity and Proceed.
    Note
    • You do not need to modify the security settings for ApsaraDB instances (such as ApsaraDB RDS for MySQL and ApsaraDB for MongoDB) and ECS-hosted databases. DTS automatically adds the CIDR blocks of DTS servers to the whitelists of ApsaraDB instances or the security group rules of ECS instances. For more information, see Add the CIDR blocks of DTS servers to the security settings of on-premises databases.
    • After data synchronization is complete, we recommend that you remove the CIDR blocks of DTS servers from the whitelists or security groups.
  5. Select the objects to migrate.
    • Basic SettingsBasic Settings
      Parameter Description
      Task Stages

      Incremental Data Synchronization is selected by default. You must also select Schema Synchronization and Full Data Synchronization. After the precheck is complete, DTS synchronizes the historical data of selected objects from the source instance to the destination cluster. The historical data is the basis for subsequent incremental synchronization.

      Processing Mode of Conflicting Tables
      • Precheck and Report Errors: checks whether the destination database contains tables that have the same names as tables in the source database. If the source and destination databases do not contain identical table names, the precheck is passed. Otherwise, an error is returned during the precheck and the data synchronization task cannot be started.

        Note You can use the object name mapping feature to rename the tables that are migrated to the destination database. You can use this feature if the source and destination databases contain identical table names and the tables in the destination database cannot be deleted or renamed. For more information, see Map object names.
      • Ignore Errors and Proceed: skips the precheck for identical table names in the source and destination databases.
        Warning If you select Ignore Errors and Proceed, data inconsistency may occur and your business may be exposed to potential risks.
        • If the source and destination databases have the same schema, and a data record has the same primary key as an existing data record in the destination database:
          • During full data synchronization, DTS does not synchronize the data record to the destination database. The existing data record in the destination database is retained.
          • During incremental data synchronization, DTS synchronizes the data record to the destination database. The existing data record in the destination database is overwritten.
        • If the source and destination databases have different schemas, initial data synchronization may fail. In this case, only part of the columns are synchronized, or the data synchronization task fails.
      DDL and DML Operations to Be Synchronized Select the SQL operations that you want to synchronize. For more information, see SQL operations that can be synchronized.
      Note To select the SQL operations performed on a specific database or table, perform the following steps: In the Selected Objects section, right-click an object. In the dialog box that appears, select the SQL operations that you want to synchronize.
      SQL Server Incremental Synchronization Mode
      • Incremental Synchronization Based on Logs of Source Database:
        • Advantages:
          • Provides low latency and good performance.
          • Provides no intrusion to the source database.
        • Disadvantages:
          • Does not support heap tables or tables without primary keys.
          • Interrupts DTS tasks due to large amounts of data written to the source database and frequent log truncation and archiving.
      • CDC-based Incremental Synchronization:
        • Advantages:
          • Supports heap tables and tables without primary keys.
          • Does not interrupt DTS tasks for log truncation in the source database.
        • Disadvantages:
          • Causes DTS to create Change Data Capture (CDC) records in the source databases and tables.
          • Causes higher latency than log-based parsing mode.
      Select Objects

      Select one or more objects from the Source Objects section and click the Rightwards arrow icon to add the objects to the Selected Objects section.

      Note In this scenario, data synchronization is performed between heterogeneous databases. Therefore, the objects to synchronize are tables, and other objects such as views, triggers and stored procedures are not synchronized to the destination database.
      Rename Databases and Tables
      • To rename an object in the destination instance, right-click the object in the Selected Objects section. For more information, see Map the name of a single object.
      • To rename multiple objects at a time in the destination instance, click Batch Edit in the upper-right corner of the Selected Objects section. For more information, see Map multiple object names at a time.
      Filter data

      You can specify WHERE conditions to filter data. For more information, see Use SQL conditions to filter data.

      Select the SQL operations to be synchronized In the Selected Objects section, right-click an object. In the dialog box that appears, select the DDL and DML operations that you want to synchronize. For more information, see SQL operations that can be synchronized.
    • Advanced SettingsAdvanced Settings
      Parameter Description
      Set Alerts
      Specifies whether to set alerts for the data synchronization task. If you select yes, DTS sends notifications to contacts if the task fails or the synchronization latency exceeds the upper limit.
      • No: does not set alerts.
      • Yes: sets alerts. In this case, you must also set the alert threshold and alert contacts.
      Retry Time for Failed Connection
      Specifies the retry time range for failed connections. Valid values: 10 to 1440. Unit: minutes. Default value: 120. We recommend that you set the retry time range to more than 30 minutes. If DTS reconnects to the source and destination databases within the specified time range, DTS resumes the data synchronization task. Otherwise, the data synchronization task fails.
      Note
      • If an instance serves as the source or destination database of multiple data synchronization tasks, the less value that is specified for the instance takes precedence.
      • When DTS retries a connection, you are charged for the DTS instance. We recommend that you specify the retry time range based on your business needs. You can also release the DTS instance at your earliest opportunity after the source and destination instances are released.
  6. In the lower part of the page, click Next: Configure Database and Table Fields. On the page that appears, set the primary key column and distribution key column of the tables that you want to synchronize to the destination AnalyticDB for MySQL cluster.
    AnalyticDB for MySQL: Specify the primary key columns and distribution keys
    Note If you select Schema Synchronization for the synchronization type, you must specify the type, primary key column, and distribution key for the tables that you want to synchronize to the AnalyticDB for MySQL V3.0 cluster. For more information, see CREATE TABLE.
  7. Click Next: Save Task Settings and Precheck in the lower part of the page.
    Note
    • Before you can start the data synchronization task, DTS performs a precheck. You can start the data synchronization task only after the task passes the precheck.
    • If the task fails to pass the precheck, you can click the Info icon icon next to each failed item to view details.
      • After you troubleshoot the issues based on the causes, you can run a precheck again.
      • If you do not need to troubleshoot the issues, you can ignore failed items and run a precheck again.
  8. Wait until the Success Rate becomes 100%. Then, click Next: Purchase Instance.
  9. On the Purchase Instance page, specify the billing method and specifications for the data synchronization instance. The following table describes related parameters.
    Section Parameter Description
    Parameters Billing method
    • Subscription: You pay for your subscription when you create an instance. The subscription billing method is more cost-effective than the pay-as-you-go billing method for long-term use.
    • Pay-as-you-go: A pay-as-you-go instance is billed on an hourly basis. For short-term use, we recommend that you select the pay-as-you-go billing method. If you no longer need a pay-as-you-go instance, you can release the instance to reduce costs.
    Instance Class DTS provides several instance classes that have different performance in synchronization speed. You can select an instance class based on your business scenario. For more information, see Specifications of data synchronization instances.
    Subscription Duration If you select the subscription billing method, set the subscription duration and the number of instances that you want to create. The subscription duration can be one to nine months or one to three years.
    Note This parameter is available only if you select the subscription billing method.
  10. Read and select Data Transmission Service (Pay-as-you-go) Service Terms.
  11. Click Buy and Start to start the data synchronization task. You can view the progress of the task in the task list.