This topic describes how to synchronize data from a self-managed SQL Server database to an AnalyticDB for PostgreSQL instance by using Data Transmission Service (DTS). The data migration feature allows you to transfer and analyze data with ease.

Prerequisites

  • You can configure a data migration task for this scenario only in the DTS console of the new version.
  • The version of the self-managed SQL Server database is 2008, 2008 R2, 2012, 2014, 2016, or 2017.
  • The destination AnalyticDB for PostgreSQL instance is created. For more information, see Create an instance.
  • The available storage space of the destination AnalyticDB for PostgreSQL instance is larger than the total size of the data in the self-managed SQL Server database.

Limits

Category Description
Limits on the source database
  • Bandwidth requirements: The server to which the source database belongs must have sufficient egress bandwidth. Otherwise, the data migration speed is affected.
  • The tables to be migrated must have PRIMARY KEY or UNIQUE constraints and all fields must be unique. Otherwise, the destination database may contain duplicate data records.
  • If you want to migrate incremental data, you must make sure that the following requirements are met:
    • The data logging feature must be enabled. The backup mode must be set to Full, and full logical backup must be performed.
    • Data logs are retained for at least 7 days during full data migration. You can wait until full data migration is complete, and then clear the data logs generated in the source database after the DTS task is run.
      Note DTS stores only 50 GB of data logs or the data logs for the last 24 hours. If the limit is exceeded, DTS automatically clears the logs that exceed the limit.
      Warning If you clear the data logs of the source database during full data migration, the task may fail to migrate incremental data. For example, full data migration takes more than 24 hours due to the large data volume in the source database and abnormal writing in the destination database. In this case, if the data logs of the source database are cleared during full data migration, DTS cannot obtain the data logs generated 24 hours ago. Therefore, the task may fail to migrate incremental data.
  • Limits on operations:
    • During schema migration and full data migration, do not perform data definition language (DDL) operations to change the schemas of databases or tables. Otherwise, the data migration task fails.
    • If you perform only full data migration, do not write data to the source database during data migration. Otherwise, data will be inconsistent between the source and destination databases. To ensure data consistency, we recommend that you select Schema Migration, Full Data Migration, and Incremental Data Migration as the migration types.
Other limits
  • DTS does not migrate data of the following types: TIMESTAMP, CURSOR, ROWVERSION, HIERACHYID, SQL_VARIANT, SPATIAL GEOMETRY, SPATIAL GEOGRAPHY, and TABLE.
  • DTS does not migrate heap tables, tables that contain non-clustered indexes, or tables that contain computed columns.
    Note If you set SQL Server Incremental Synchronization Mode to CDC-based Incremental Synchronization in the Configure Objects and Advanced Settings step, heap tables and tables that contain non-clustered indexes can be migrated.
  • To ensure that the delay time of incremental data migration is accurate, DTS adds a heartbeat table to the self-managed SQL Server database. The name of the heartbeat table is Source table name_dts_mysql_heartbeat.
  • Before you migrate data, evaluate the impact of data migration on the performance of the source and destination databases. We recommend that you migrate data during off-peak hours. During full data migration, DTS uses read and write resources of the source and destination databases. This may increase the loads of the database servers.
  • During full data migration, concurrent INSERT operations cause fragmentation in the tables of the destination database. After full data migration is complete, the tablespace of the destination database is larger than that of the source database.
  • You must make sure that the precision settings for columns of the FLOAT or DOUBLE data type meets your business requirements. DTS uses the ROUND(COLUMN,PRECISION) function to retrieve values from columns of the FLOAT or DOUBLE data type. If you do not specify a precision, DTS sets the precision for the FLOAT data type to 38 digits and the precision for the DOUBLE data type to 308 digits.
  • DTS attempts to resume data migration tasks that failed within the last seven days. Before you switch workloads to the destination instance, stop or release the data migration task. You can also run the revoke command to revoke the write permissions from the accounts that are used by DTS to access the destination instance. Otherwise, the data in the source database will overwrite the data in the destination instance after the task is resumed.

Migration types

  • Schema migration

    DTS migrates the schemas of the required objects from the source database to the destination database.

    • DTS supports schema migration for the following types of objects: schema, table, view, function, and procedure.
    • DTS does not migrate 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.
    Warning SQL Server and AnalyticDB for PostgreSQL are heterogeneous databases. Their data types 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 between heterogeneous databases.
  • Full data migration

    DTS migrates historical data of the required objects from the source database to the destination database.

  • Incremental data migration

    After full data migration is complete, DTS migrates incremental data from the source database to the destination database. Incremental data migration allows you to ensure service continuity when you migrate data between self-managed databases.

SQL operations that can be migrated

Operation type SQL statements
DML INSERT, UPDATE, and DELETE
DDL ADD COLUMN

Permissions required for database accounts

Database Schema migration Full data migration Incremental data migration
Self-managed SQL Server database The SELECT permission The SELECT permission The permissions of the sysadmin role
AnalyticDB for PostgreSQL instance
  • The LOGIN permission
  • The SELECT, CREATE, INSERT, UPDATE, and DELETE permissions on the destination tables
  • The CONNECT and CREATE permissions on the destination database
  • The CREATE permission on the destination schemas
  • The COPY permission (the permission to perform memory-based batch copy operations)
Note You can use the initial account of the AnalyticDB for PostgreSQL instance.
For more information about how to create and authorize a database account, see the following topics:

Before you begin

Note Before you configure a task to migrate incremental data, you must configure log settings on the self-managed SQL Server database and create clustered indexes.
Warning If you need to migrate incremental data from multiple databases, repeat Steps 1 to 4 for each database.
  1. Run the following command in the self-managed SQL Server database to change the recovery model to full:
    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 back up the log entries of 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 a clustered index for each source table. For more information, see Create Clustered Indexes.

Procedure

  1. Go to the Data Migration 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 Migration.
  2. In the upper-left corner of the page, select the region where the data migration instance resides.
    Select a 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 at the top of the page. This ensures that you can create and run the data migration task.
    Configure the source and destination databases
    Section Parameter Description
    N/A Task Name

    DTS automatically generates a task name. We recommend that you specify an informative name that helps identify the task. The task name does not need to be unique.

    Source Database Database Type Select SQL Server.
    Access Method Select Self-managed Database on ECS.
    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.
    Instance Region Select the region where the self-managed SQL Server database resides.
    ECS Instance ID Enter the ID of the Elastic Compute Service (ECS) instance that hosts 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 that is used to log on to the self-managed SQL Server database. For information about the permissions that are required for the account, see Permissions required for database accounts.
    Database Password

    Enter the password of the database account.

    Destination Database Database Type Select AnalyticDB for PostgreSQL.
    Access Method Select Alibaba Cloud Instance.
    Instance Region Select the region where the destination AnalyticDB for PostgreSQL instance resides.
    Instance ID Select the ID of the destination AnalyticDB for PostgreSQL instance.
    Database Name Enter the name of the destination database in the AnalyticDB for PostgreSQL instance.
    Database Account Enter the database account of the destination AnalyticDB for PostgreSQL instance. For information about the permissions that are required for the account, see Permissions required for database accounts.
    Database Password

    Enter the password of the database account.

  4. If a whitelist is configured for your self-managed database, you must add the CIDR blocks of DTS servers to the whitelist. Then, click Test Connectivity and Proceed.
  5. Select objects for the task and configure advanced settings.
    • Basic Settings
      Parameter Description
      Task Stages
      • To perform only full data migration, select Schema Migration and Full Data Migration.
      • To ensure service continuity during data migration, select Schema Migration, Full Data Migration, and Incremental Data Migration.
      Note If Incremental Data Migration is not selected, we recommend that you do not write data to the source instance during data migration. This ensures data consistency between the source and destination instances.
      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 migration 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.
      • 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, DTS does not migrate data records that have the same primary keys as data records in the destination database.
        • If the source and destination databases have different schemas, only some columns are migrated or the data migration 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.
      • Incremental Synchronization Based on Logs of Source Database:
        • 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.
      DDL and DML Operations to Be Synchronized Select the SQL operations that you want to migrate at the instance level. For more information, see
      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 migrate.
      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 columns, tables, or databases as the objects to be migrated. If you select tables or columns as the objects to be migrated, DTS does not migrate other objects such as views, triggers, and stored procedures to the destination database.
      Rename Databases and Tables
      • To rename an object that you want to migrate to the destination instance, right-click the object in the Selected Objects section.
      • To rename multiple objects at a time, click Batch Edit in the upper-right corner of the Selected Objects section.
      Note If you use the object name mapping feature to rename an object, other objects that are dependent on the object may fail to be migrated.
      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 migrated 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 migrate. For more information, see SQL operations that can be migrated.
    • Advanced SettingsAdvanced Settings
      Parameter Description
      Set Alerts
      Specify whether to set alerts for the data migration task. If the task fails or the migration 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 migration task. Otherwise, the data migration 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. Specify the primary key column and distribution key of the table that you want to migrate to the AnalyticDB for PostgreSQL instance.
    AnalyticDB for PostgreSQL: Specify the primary key column and distribution key
  7. In the lower part of the page, click Next: Precheck and Start Task.
    Note
    • Before you can start the data migration task, DTS performs a precheck. You can start the data migration 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.
  8. Wait until the Success Rate becomes 100%. Then, click Next: Purchase Instance.
  9. On the Purchase Instance page, specify the Instance Class parameter for the data migration instance. The following table describes the parameter.
    Section Parameter Description
    Parameters Instance Class

    DTS provides several instance classes that have different performance in migration speed. You can select an instance class based on your business scenario. For more information, see Specifications of data migration instances.

  10. Read and select Data Transmission Service (Pay-as-you-go) Service Terms.
  11. Click Buy and Start to start the data migration task. You can view the progress of the task in the task list.