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

Prerequisites

• The version of the self-managed SQL Server database is supported by DTS. For more information, see Overview of data synchronization scenarios.
• The destination AnalyticDB for PostgreSQL instance is created. For more information, see Create an AnalyticDB for PostgreSQL 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

Billing

Supported synchronization topologies

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

SQL operations that can be synchronized

Permissions required for database accounts

Preparations

1. Execute the following statement 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. 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 create a logging 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. Incremental data synchronization by parsing logs of the source database is not supported for heap tables,tables without primary keys, compressed tables, and tables with calculated columns. You can execute the following SQL statements to check whether the source database contains the preceding table types:
   1. Check for heap tables.

      select s.name, t.name from sys.schemas s inner join sys.tables t on s.schema_id = t.schema_id where t.type = 'U' and t.object_id in (select object_id from sys.indexes where index_id = 0)

   2. Check for tables without primary keys.

      select s.name, t.name from sys.schemas s inner join sys.tables t on s.schema_id = t.schema_id where t.type = 'U' and t.object_id not in (select parent_object_id from sys.objects where type = 'PK')

   3. Check for compressed tables.

      select s.name as schema_name,t.name as table_name from sys.objects t, sys.schemas s, sys.partitions i where s.schema_id=t.schema_id and t.object_id = i.object_id and i.data_compression != 0

   4. Check for tables with calculated columns.

      select s.name, t.name from sys.schemas s inner join sys.tables t on s.schema_id = t.schema_id where t.type = 'U' and t.object_id in (select object_id from [%s].sys.columns where is_computed = 1)

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.
   
3. Click Create Task. On the page that appears, 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 Self-managed Database on ECS.
   	Instance Region	The region where 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.
   	Database Account	The account of 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	The password of the database account.
   	Encryption	Select Non-encrypted or SSL-encrypted based on your requirements.
   Destination Database	Database Type	Select AnalyticDB for PostgreSQL.
   	Access Method	Select Cloud Instance.
   	Instance Region	The region where the destination AnalyticDB for PostgreSQL instance resides.
   	Instance ID	The ID of the destination AnalyticDB for PostgreSQL cluster.
   	Database Name	The name of the destination database in the AnalyticDB for PostgreSQL instance.
   	Database Account	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	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 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	The DDL and DML 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 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 DML and DDL operations to synchronize. For more information, see SQL operations that can be synchronized.

   • Advanced 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 column of the tables that you want to synchronize to the destination AnalyticDB for PostgreSQL instance.
   
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 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.