Data Transmission Service:Migrate data from a self-managed SQL Server database to an AnalyticDB for PostgreSQL instance

Prerequisites

• You can configure a data migration task for this scenario only in the new DTS console.
• The version of the self-managed SQL Server database is supported by DTS. For more information, see Overview of data migration scenarios.
• 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.
• If the source database is in the following conditions, we recommend that you migrate data by using the backup feature of ApsaraDB RDS for SQL Server. For more information, see Migrate data from a self-managed database to ApsaraDB RDS for SQL Server.
  • The source instance contains more than 10 databases.
  • A single database of the source instance backs up its logs at an interval of less than 1 hour.
  • A single database of the source instance executes more than 100 DDL statements each hour.
  • Logs are written at a rate of 20 MB/s for a single database of the source instance.
  • The change data capture (CDC) feature needs to be enabled for more than 1,000 tables in the source ApsaraDB RDS for SQL Server instance.
  • The logs of a database in the source ApsaraDB RDS for SQL Server instance involve heap tables, tables without primary keys, compressed tables, or tables with computed columns. You can execute the following SQL statements to check whether the source database contains these tables.
    1. Execute the following SQL statement to check for heap tables:

       SELECT s.name AS schema_name, t.name AS table_name FROM sys.schemas s INNER JOIN sys.tables t ON s.schema_id = t.schema_id AND t.type = 'U' AND s.name NOT IN ('cdc', 'sys') AND t.name NOT IN ('systranschemas') AND t.object_id IN (SELECT object_id FROM sys.indexes WHERE index_id = 0);

    2. Execute the following SQL statement to check for tables without primary keys:

       SELECT s.name AS schema_name, t.name AS table_name FROM sys.schemas s INNER JOIN sys.tables t ON s.schema_id = t.schema_id AND t.type = 'U' AND s.name NOT IN ('cdc', 'sys') AND t.name NOT IN ('systranschemas') AND t.object_id NOT IN (SELECT parent_object_id FROM sys.objects WHERE type = 'PK');

    3. Execute the following SQL statement to check for primary key columns contained in clustered index columns:

       SELECT s.name AS schema_name, t.name AS table_name FROM sys.schemas s INNER JOIN sys.tables t ON s.schema_id= t.schema_id WHERE t.type= 'U' AND s.name NOT IN('cdc', 'sys')  AND t.name NOT IN('systranschemas')  AND t.object_id IN (SELECT pk_columns.object_id AS object_id FROM (select sic.object_id object_id, sic.column_id FROM sys.index_columns sic, sys.indexes sis WHERE sic.object_id= sis.object_id AND sic.index_id= sis.index_id AND sis.is_primary_key= 'true') pk_columns LEFT JOIN (SELECT sic.object_id object_id, sic.column_id FROM sys.index_columns sic, sys.indexes sis WHERE sic.object_id= sis.object_id AND sic.index_id= sis.index_id AND sis.index_id= 1) cluster_colums ON pk_columns.object_id= cluster_colums.object_id WHERE pk_columns.column_id != cluster_colums.column_id);

    4. Execute the following SQL statement to check for compressed tables:

       SELECT s.name AS schema_name, t.name AS table_name FROM sys.objects t, sys.schemas s, sys.partitions p WHERE s.schema_id = t.schema_id AND t.type = 'U' AND s.name NOT IN ('cdc', 'sys') AND t.name NOT IN ('systranschemas') AND t.object_id = p.object_id AND p.data_compression != 0;

    5. Execute the following SQL statement to check for tables with computed columns:

       SELECT s.name AS schema_name, t.name AS table_name FROM sys.schemas s INNER JOIN sys.tables t ON s.schema_id = t.schema_id AND t.type = 'U' AND s.name NOT IN ('cdc', 'sys') AND t.name NOT IN ('systranschemas') AND t.object_id IN (SELECT object_id FROM sys.columns WHERE is_computed = 1);

Limits

Billing

Migration types

• Schema migration

  DTS migrates the schemas of 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, Common Language Runtime (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. 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 between heterogeneous databases.
• Full data migration

  DTS migrates the historical data of 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 data to be migrated smoothly without interrupting services of self-managed applications during data migration.

SQL operations that can be migrated during incremental data migration

Permissions required for database accounts

• Self-managed SQL Server database: CREATE USER and GRANT (Transact-SQL)
• AnalyticDB for PostgreSQL instance: Create a database account and Manage users and permissions

Preparations

1. Execute the following statements on 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

   Parameter:

   <database_name>: the name of the source database.

   Example:

   use master;
   GO
   ALTER DATABASE mytestdata SET RECOVERY FULL WITH ROLLBACK IMMEDIATE;
   GO

2. Execute the following statement 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. Execute the following statement 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

Procedure

1. Go to the Data Migration Tasks page.
   1. Log on to the Data Management (DMS) console.
   2. In the top navigation bar, click DTS.
   3. In the left-side navigation pane, choose DTS (DTS) > Data Migration.
   Note You can also go to the Data Migration Tasks page of the new DTS console.
2. From the drop-down list next to Data Migration Tasks, select the region in which your data migration instance resides.
   Note If you use the new DTS console, select the region in which the data migration instance resides in the upper-left corner.
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 the data migration task can be successfully created and run.

   Section	Parameter	Description
   N/A	Task Name	The name of the task. DTS automatically generates a task name. We recommend that you specify an informative name to identify the task. You do not need to specify a unique task name.
   Source Database	Database Type	The type of the source database. Select SQL Server.
   	Access Method	The access method of the source database. 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	The region in which the self-managed SQL Server database resides.
   	ECS Instance ID	The ID of the Elastic Compute Service (ECS) instance that hosts the self-managed SQL Server database.
   	Port Number	The service port number of the self-managed SQL Server database. The default port number is 1433.
   	Database Account	The account that is used to log on to the self-managed SQL Server database. For more information about the permissions that are required for the account, see the Permissions required for database accounts section of this topic.
   	Database Password	The password of the database account.
   Destination Database	Database Type	The type of the destination database. Select AnalyticDB for PostgreSQL.
   	Access Method	The access method of the destination database. Select Alibaba Cloud Instance.
   	Instance Region	The region in which the destination AnalyticDB for PostgreSQL instance resides.
   	Instance ID	The ID of the destination AnalyticDB for PostgreSQL instance.
   	Database Name	The name of the destination database in the destination AnalyticDB for PostgreSQL instance.
   	Database Account	The database account of the destination AnalyticDB for PostgreSQL instance. For more information about the permissions that are required for the account, see the Permissions required for database accounts section of this topic.
   	Database Password	The password of the database account.

4. If a whitelist is configured for your self-managed database, add the CIDR blocks of DTS servers to the whitelist. Then, click Test Connectivity and Proceed.
   Warning

   • If the source or destination database is an Alibaba Cloud database instance, such as an ApsaraDB RDS for MySQL or ApsaraDB for MongoDB, DTS automatically adds the CIDR blocks of DTS servers to the whitelist of the instance. For more information, see Add the CIDR blocks of DTS servers to the security settings of on-premises databases. If the source or destination database is a self-managed database hosted on an Elastic Compute Service (ECS) instance, DTS automatically adds the CIDR blocks of DTS servers to the security group rules of the ECS instance, and you need to manually add the CIDR blocks of DTS servers to the whitelist of the self-managed database on the ECS instance to allow DTS to access the database. If the source or destination database is a self-managed database that is deployed in a data center or provided by a third-party cloud service provider, you must manually add the CIDR blocks of DTS servers to the whitelist of the database to allow DTS to access the database.
   • If the CIDR blocks of DTS servers are automatically or manually added to the whitelist or ECS security group rules, security risks may arise. Therefore, before you use DTS to migrate data, you must understand and acknowledge the potential risks and take preventive measures, including but not limited to the following measures: enhancing the security of your username and password, limiting the ports that are exposed, authenticating API calls, regularly checking the whitelist or ECS security group rules and forbidding unauthorized CIDR blocks, or connecting the database to DTS by using Express Connect, VPN Gateway, or Smart Access Gateway.
   • After the DTS task is complete or released, we recommend that you manually remove the CIDR blocks from the whitelist or ECS security group rules. You must remove the IP address whitelist group whose name contains dts from the whitelist of the Alibaba Cloud database instance or the security group rules of the ECS instance. For more information about the CIDR blocks that you must remove from the whitelist of the self-managed databases that are deployed in data centers or databases that are hosted on third-party cloud services, see Add the CIDR blocks of DTS servers to the security settings of on-premises databases.
5. Configure objects to migrate and advanced settings.
   • Basic Settings

     Parameter or setting	Description
     Migration Type	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 tables that have the same names, the precheck is passed. Otherwise, an error is returned during the 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 tables that have identical 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, 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	Log-based Parsing for Non-heap Tables and CDC-based Incremental Synchronization for Heap Tables: Advantages: Supports heap tables, tables without primary keys, compressed tables, and tables with computed columns. Provides higher stability and a variety of complete DDL statements. Disadvantage: DTS creates the trigger dts_cdc_sync_ddl, the heartbeat table dts_sync_progress, and the DDL storage table dts_cdc_ddl_history in the source database and enables Change Data Capture (CDC) for the source database and specific tables. Incremental Synchronization Based on Logs of Source Database: Advantages: Provides no intrusion to the source database. Disadvantage: Does not support heap tables, tables without primary keys, compressed tables, or tables with computed columns.
     DDL and DML Operations to Be Synchronized	The SQL operations to be migrated at the instance level. For more information, see the SQL operations that can be migrated during incremental data migration section of this topic. 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 incrementally migrate.
     Select Objects	Select one or more objects from the Source Objects section and click the icon to add the objects to the Selected Objects section. Note In this scenario, data migration is performed between heterogeneous databases. Therefore, only tables can be migrated. Other objects such as views, triggers, or stored procedures are not migrated 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. For more information, see Map the name of a single object. To rename multiple objects at a time, click in the upper-right corner of the Selected Objects section. For more information, see Map multiple object names at a time. 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 incrementally migrated	In the Selected Objects section, right-click an object. In the dialog box that appears, select the SQL operations that you want to migrate. For more information about the SQL operations that can be migrated, see the SQL operations that can be migrated during incremental data migration section of this topic.

   • Advanced Settings

     Parameter	Description
     Set Alerts	Specifies 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. Valid values: No: does not set alerts. Yes: sets alerts. If you select Yes, you must also set the alert threshold and alert contacts. For more information, see Configure monitoring and alerting when you create a DTS task.
     Retry Time for Failed Connections	The retry time range for failed connections. If the source or destination database fails to be connected after the data migration task is started, DTS immediately retries a connection within the time range. Valid values: 10 to 1440. Unit: minutes. Default value: 720. We recommend that you set the parameter to a value greater than 30. If DTS reconnects to the source and destination databases within the specified time range, DTS resumes the data migration task. Otherwise, the data migration task fails. Note If you set different retry time ranges for multiple data migration tasks that share the same source or destination database, the value that is set later takes precedence. If DTS retries a connection, you are charged for the operation of the DTS instance. We recommend that you specify the retry time based on your business needs and release the DTS instance at your earliest opportunity after the source and destination instances are released.

6. Specify the primary key columns and distribution key columns of the tables that you want to migrate to the AnalyticDB for PostgreSQL instance.
   
7. In the lower part of the page, click Next: Save Task Settings and Precheck.
   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, click View Details next to each failed item. After you troubleshoot the issues based on the causes, run a precheck again.
   • If an alert is triggered for an item during the precheck:
     • If an alert item cannot be ignored, click View Details next to the failed item and troubleshoot the issues. Then, run a precheck again.
     • If an alert item can be ignored, click Confirm Alert Details. In the View Details dialog box, click Ignore. In the message that appears, click OK. Then, click Precheck Again to run a precheck again. If you ignore the alert item, data inconsistency may occur, and your business may be exposed to potential risks.
8. Wait until the Success Rate value 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
   New Instance Class	Instance Class	DTS provides several instance classes that vary in the 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 the check box to agree to 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.