This topic describes how to synchronize data from a self-managed SQL Server database to a PolarDB for MySQL cluster by using Data Transmission Service (DTS).

Prerequisites

  • The version of the self-managed SQL Server database is 2017, 2016, 2014, 2012, 2008, or 2008 R2.
  • The destination PolarDB for MySQL cluster is created. For more information, see Purchase a pay-as-you-go cluster and Purchase a subscription cluster.
  • The available storage space of the PolarDB for MySQL cluster is larger than the total size of the data in the self-managed SQL Server database.

Limits

Supported synchronization topologies

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

SQL operations that can be synchronized

Operation type SQL statements
DML INSERT, UPDATE, and DELETE

Before you begin

Before you configure a data synchronization task, configure log settings and create clustered indexes on the self-managed SQL Server database.
Warning If you need to synchronize incremental data from multiple databases, repeat Steps 1 to 4 for each database.
  1. Run the following command on the self-managed SQL Server database to change the recovery model to full. You can also change the recovery model by using SQL Server Management Studio (SSMS). For more information, see View or Change the Recovery Model of a Database (SQL Server).
    use master;
    GO
    ALTER DATABASE <database_name> SET RECOVERY FULL WITH ROLLBACK IMMEDIATE;
    GO
    Parameters:

    <database_name>: the name of the source database.

    Example:
    use master;
    GO
    ALTER DATABASE mytestdata SET RECOVERY FULL WITH ROLLBACK IMMEDIATE;
    GO
  2. Run the following command to create a logical backup for the source database. Skip this step if you have already created a logical backup.
    BACKUP DATABASE <database_name> TO DISK='<physical_backup_device_name>';
    GO
    Parameters:
    • <database_name>: the name of the source database.
    • <physical_backup_device_name>: the storage path and file name of the backup file.
    Example:
    BACKUP DATABASE mytestdata TO DISK='D:\backup\dbdata.bak';
    GO
  3. Run the following command to create a logical backup for the source database.
    BACKUP LOG <database_name> to DISK='<physical_backup_device_name>' WITH init;
    GO
    Parameters:
    • <database_name>: the name of the source database.
    • <physical_backup_device_name>: the storage path and file name of the backup file.
    Example:
    BACKUP LOG mytestdata TO DISK='D:\backup\dblog.bak' WITH init;
    GO
  4. Create clustered indexes for the tables that you want to synchronize. For more information, see Create Clustered Indexes.

Procedure

  1. Go to the Data Synchronization page of the new DTS console.
    Note You can also log on to the Data Management (DMS) console. In the top navigation bar, choose DTS > Data Synchronization.
  2. In the upper-left corner of the page, select the region where the data synchronization instance resides.
    Select a region
  3. Click Create Task. On the page that appears, configure the source and destination databases.
    源目库配置
    Section Parameter Description
    N/A Task Name

    DTS automatically generates a task name. We recommend that you specify an informative name to identify the task. You do not need to use a unique task name.

    Source Database Database Type Select SQL Server.
    Access Method Select Self-managed Database Connected Over Express Connect, VPN Gateway, or Smart Access Gateway.
    Instance Region Select the region where the self-managed SQL Server database resides.
    Note If your source database is a self-managed database, you must deploy the network environment for the database. For more information, see Preparation overview.
    Replicate Data Across Alibaba Cloud Accounts In this example, select No because data is synchronized within the same Alibaba Cloud account.
    Connected VPC Select the ID of the virtual private cloud (VPC) that is connected to the self-managed SQL Server database.
    IP Address Enter the server IP address of the self-managed SQL Server database.
    Port Number Enter the service port number of the self-managed SQL Server database. The default port number is 1433.
    Database Account Enter the account of the self-managed SQL Server database. The account must have the permissions of the sysadmin role. For more information, see CREATE USER and GRANT (Transact-SQL).
    Database Password

    Enter the password of the database account.

    Destination Database Database Type Select PolarDB for MySQL.
    Access Method Select Alibaba Cloud Instance.
    Instance Region Select the region where the destination PolarDB for MySQL cluster resides.
    PolarDB Cluster ID Select the ID of the destination PolarDB for MySQL cluster.
    Database Account Enter the database account of the destination PolarDB for MySQL cluster. The account must have the read and write permissions.
    Database Password

    Enter the password of the database account.

  4. In the lower part of the page, click Test Connectivity and Proceed.
  5. Select objects for the task and configure advanced settings.
    • Basic Settings基础配置
      Parameter Description
      Task Stages

      Incremental Data Synchronization is selected by default. You must also select Schema Synchronization and Full Data Synchronization. After the precheck, DTS synchronizes the historical data of the 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 precheck and the data synchronization task cannot be started.
        Note You can use the object name mapping feature to rename the tables that are synchronized 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 consistency is not guaranteed 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, data may fail to be initialized. In this case, only some columns are synchronized or the data synchronization task fails.
      SQL Server Incremental Synchronization Mode
      • Incremental Synchronization Based on Logs of Source Database:
        • Advantages:
          • Low latency and good performance
          • No intrusion to the source database
        • Disadvantages:
          • Heap tables and tables without primary keys are not supported.
          • DTS tasks may be interrupted due to large volumes of data written to the source database and frequent log truncation and archiving.
      • CDC-based Incremental Synchronization:
        • Advantages:
          • Heap tables and tables without primary keys are supported.
          • Log truncation in the source database does not interrupt DTS tasks.
        • Disadvantages:
          • DTS creates Change Data Capture (CDC) records in the source databases and tables.
          • The latency of this mode is higher than the log-based parsing mode.
      Select Objects

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

      Note You can select tables or databases as the objects to be synchronized.
      Rename Databases and Tables
      • To rename an object that you want to synchronize to 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, 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 SQL operations that you want to synchronize. For more information, see SQL operations that can be synchronized.
    • Advanced Settings高级配置
      Parameter Description
      Set Alerts
      Specify whether to set alerts for the data synchronization task. If the task fails or the synchronization latency exceeds the threshold, the alert contacts will receive notifications.
      • Select No if you do not want to set alerts.
      • Select Yes to set alerts. In this case, you must also set the alert threshold and alert contacts.
      Retry Time for Failed Connections
      Specify the retry time for failed connections. Valid values: 10 to 1440. Unit: minutes. Default value: 120. We recommend that you set the retry time to more than 30 minutes. If DTS reconnects to the source and destination databases within the specified time, DTS resumes the data synchronization task. Otherwise, the data synchronization task fails.
      Note
      • If multiple DTS instances have the same source or destination database, the lowest value takes effect. For example, the retry time is set to 30 minutes for Instance A and 60 minutes for Instance B, DTS retries failed connections at an interval of 30 minutes.
      • When DTS retries a connection, you are charged for the DTS instance. We recommend that you specify the retry time 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. 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.
      • You can troubleshoot the issues based on the causes and run a precheck again.
      • If you do not need to troubleshoot the issues, you can ignore failed items and run a precheck again.
  7. Wait until the Success Rate becomes 100%. Then, click Next: Purchase Instance.
  8. On the Purchase Instance page, specify the Billing Method and Instance Class parameters for the data synchronization instance. The following table describes the parameters.
    Section Parameter Description
    Parameters Billing Method
    • Subscription: You can pay for your subscription when you create an instance. We recommend that you select the subscription billing method for long-term use because it is more cost-effective than the pay-as-you-go billing method. You can save more costs with longer subscription periods.
    • Pay-as-you-go: A pay-as-you-go instance is billed on an hourly basis. We recommend that you select the pay-as-you-go billing method for short-term use. If you no longer require your pay-as-you-go instance, you can release it 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 Length If you select the subscription billing method, set the subscription length and the number of instances that you want to create. The subscription length can be one to nine months or one to three years.
    Note This parameter is available only if you select the subscription billing method.
  9. Read and select Data Transmission Service (Pay-as-you-go) Service Terms.
  10. Click Buy and Start to start the data synchronization task. You can view the progress of the task in the task list.