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

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).

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 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 ApsaraDB RDS for SQL Server instance meets one of the following conditions, we recommend that you split the synchronization task into multiple subtasks:
- 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.

Limits

Note

During schema synchronization, DTS synchronizes foreign keys from the source database to the destination database.
During full data synchronization and incremental data synchronization, DTS temporarily disables the constraint check and cascade operations on foreign keys at the session level. If you perform the cascade update and delete operations on the source database during data synchronization, data inconsistency may occur.

Category	Description
Limits on the source database	The tables to be synchronized 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 be synchronized and you want to edit the table (such as renaming tables or columns) in the destination database, you can synchronize up to 5,000 tables in a single data synchronization task. If you run a task to synchronize more than 5,000 tables, a request error occurs. In this case, we recommend that you configure multiple tasks to synchronize the tables in batches 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 configure multiple tasks to synchronize the tables. 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. Otherwise, DTS may fail to obtain the data logs and the task may fail. In exceptional circumstances, data inconsistency or loss may occur. After the full data synchronization is complete, you can set the retention period to more than 24 hours. Make sure that you set the retention period of data logs based on the preceding requirements. Otherwise, the Service Level Agreement (SLA) of DTS does not guarantee service reliability or performance. If Change Data Capture (CDC) needs to be enabled for the tables to be synchronized from the source database, make sure that the tables meet the following requirements. Otherwise, the precheck fails. The value of the srvname field in the sys.sysservers view is the same as the return value of the SERVERPROPERTY function. If the source database is a self-managed SQL Server database, the database owner must be the sa user. If the source database is an ApsaraDB RDS for SQL Server database, the database owner must be the sqlsa user. If the source database is of Enterprise Edition, you must use SQL Server 2008 or later. If the source database is of Standard Edition, you must use SQL Server 2016 SP1 or later. If the source database is of Standard Edition or Enterprise Edition and its version is SQL Server 2017, we recommend that you update the version.
Other limits	Requirements for the objects to be synchronized: DTS supports initial schema synchronization for the following types of objects: schema, table, view, function, and procedure. Warning The source and destination databases are heterogeneous databases. The data types that they support do not have one-to-one correspondence. In this case, the task may fail or data loss may occur. 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 be synchronized must have clustered indexes that contain primary key columns. In addition, the tables to be synchronized cannot be heap tables, compressed tables, tables without primary keys, or tables with computed columns. Ignore the preceding limits in the hybrid log-based parsing mode. Note For more information about how to view table information, see How do I view information about heap tables, tables without primary keys, compressed tables, and tables that contain computed columns in an SQL Server database?. 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 hybrid log-based parsing incremental synchronization mode, DTS creates a trigger named dts_cdc_sync_ddl, a heartbeat table named dts_sync_progress, and a DDL history table named dts_cdc_ddl_history by using DDL and enables CDC for the database and some tables. We recommend that you set the upper limit of the number of requests per second to 1000 for the tables for which CDC is enabled in the source database. 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 initial full data synchronization, DTS uses the read and write resources of the source and destination databases. This may increase the loads on the database servers. During initial full data synchronization, concurrent INSERT operations cause fragmentation in the tables of the destination database. After the initial full data synchronization is complete, the size of used tablespace of the destination database is larger than that of the source database. 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. For example, 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. If the data synchronization task involves incremental data synchronization, DTS does not allow you to perform the reindexing operation. If you perform the reindexing operation, the data synchronization task may fail, or even data loss may occur. If the number of tables for which CDC is enabled exceeds 1,000 in a data synchronization task, the precheck fails.

Billing

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

Supported synchronization topologies

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

For more information about the synchronization topologies that are supported by DTS, 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 operation creates a partitioned table or a table that contains functions, DTS does not synchronize the operation. ADD COLUMN and DROP COLUMN DROP TABLE CREATE INDEX and DROP INDEX Note DTS does not synchronize DDL operations that contain user-defined types. DTS does not synchronize transactional DDL operations.

Permissions required for database accounts

Database	Required permissions	References
Self-managed SQL Server database	sysadmin	CREATE USER and GRANT (Transact-SQL)
AnalyticDB for PostgreSQL instance	LOGIN permission SELECT, CREATE, INSERT, UPDATE, and DELETE permissions on the destination tables CONNECT and CREATE permissions on the destination database CREATE permission on the destination schemas COPY permission (the permission to perform memory-based batch copy operations) Note You can use the initial account of the AnalyticDB for PostgreSQL instance.	Create a database account and Manage users and permissions

Preparations

Before you configure a data synchronization task, configure log settings and create clustered indexes on the self-managed SQL Server database.

Important If you need to synchronize data from multiple databases, repeat Steps 1 to 3 for each database. Otherwise, data inconsistency may occur.

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
```
Parameter:
<database_name>: the name of the source database.
Example:
```
use master;
GO
ALTER DATABASE mytestdata SET RECOVERY FULL WITH ROLLBACK IMMEDIATE;
GO
```
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
```
Parameter:
- <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
```
Execute the following statement to create a log backup for the source database.
```
BACKUP LOG <database_name> to DISK='<physical_backup_device_name>' WITH init;
GO
```
Parameter:
- <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

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, click DTS. In the left-side navigation pane, choose DTS (DTS) > Data Synchronization.
In the upper-left corner of the page, select the region in which you want to create the data synchronization task.

Click Create Task. On the page that appears, configure the source and destination databases.

Section	Parameter	Description
N/A	Task Name	The name of the task. DTS automatically assigns a name to the task. We recommend that you specify a descriptive name that makes it easy 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.
	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.
	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	Specifies whether to encrypt the connection to the database. Select Non-encrypted or SSL-encrypted based on your business requirements.
Destination Database	Database Type	The type of the destination database. Select AnalyticDB 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 cluster 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 information about the permissions that are required for the account, see Permissions required for database accounts.
	Database Password	The password of the database account.

In the lower part of the page, click Test Connectivity and Proceed.
If the source or destination database is an Alibaba Cloud database instance, such as an ApsaraDB RDS for MySQL or ApsaraDB for MongoDB instance, DTS automatically adds the CIDR blocks of DTS servers to the whitelist of the instance. 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 must ensure that the ECS instance can 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. For more information, see Add the CIDR blocks of DTS servers to the security settings of on-premises databases.
Warning
If the CIDR blocks of DTS servers are automatically or manually added to the whitelist of the database or instance, or to the ECS security group rules, security risks may arise. Therefore, before you use DTS to synchronize 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.

Configure objects to synchronize and advanced settings.

Parameter	Description
Synchronization Type	By default, Incremental Data Synchronization is selected. 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 instance. 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 tables that have 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 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 inconsistency may occur, and your business may be exposed to potential risks. If the source and destination databases have the same schemas, and a data record has the same primary key value 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, only some columns are synchronized, or the data synchronization task fails. Operate with caution. Precheck and Report Errors: checks whether the destination database contains collections that have the same names as collections in the source database. If the source and destination databases do not contain collections that have identical collection 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 collections that are synchronized to the destination database. You can use this feature if the source and destination databases contain collections that have identical names and the collections in the destination database cannot be deleted or renamed. For more information, see Rename an object to be synchronized. Ignore Errors and Proceed: skips the precheck for identical collection 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. DTS does not synchronize data records that have the same primary key values as data records in the destination database. Data may fail to be initialized, only some columns are synchronized, or the data synchronization task fails. 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 identical table names, the precheck is passed. Otherwise, an error is returned during the precheck and the data synchronization task cannot be started. 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 schemas, and a data record has the same primary key value 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, only some columns are synchronized, or the data synchronization task fails. Operate with caution.
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	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. Disadvantages: 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. Does not support the SELECT INTO statement on CDC-enabled tables in the source database. The triggers created by DTS in the source database cannot be manually deleted. Incremental Synchronization Based on Logs of Source Database: Advantage: Does not modify the settings of the source database. Disadvantage: Does not support heap tables, tables without primary keys, compressed tables, or tables with computed columns.
Source 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, only tables can be synchronized. Other objects such as views, triggers, or stored procedures are not synchronized to the destination database.
Selected Objects	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. Note To select the SQL operations performed on a specific database or table, right-click an object in the Selected Objects section. 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. To specify WHERE conditions to filter data, right-click a table in the Selected Objects section. In the dialog box that appears, specify the conditions. For more information, see Use SQL conditions to filter data. If you use the object name mapping feature to rename an object, other objects that are dependent on the object may fail to be synchronized.

Click Next: Advanced Settings to configure advanced settings.

Parameter	Description
Set Alerts	Specifies whether to configure alerting for the data synchronization task. If the task fails or the synchronization latency exceeds the specified threshold, alert contacts will receive notifications. Valid values: No: does not configure alerting. Yes: configures alerting. In this case, you must also configure the alert threshold and alert contacts. For more information, see Configure monitoring and alerting when you create a DTS task.
Specify the retry time range for failed connections	The retry time range for failed connections. If the source or destination database fails to be connected after the data synchronization 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 synchronization task. Otherwise, the data synchronization task fails. Note If you set different retry time ranges for multiple DTS tasks that have the same source or destination database, the shortest retry time range that is set 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 requirements. You can also release the DTS instance at your earliest opportunity after the source and destination instances are released.
The wait time before a retry when other issues occur in the source and destination databases.	The retry time range for other issues. For example, if the DDL or DML operations fail to be performed after the data synchronization task is started, DTS immediately retries the operations within the time range. Valid values: 1 to 1440. Unit: minutes. Default value: 10. We recommend that you set the parameter to a value greater than 10. If the failed operations are successfully performed within the specified time range, DTS resumes the data synchronization task. Otherwise, the data synchronization task fails. Important The value of the The wait time before a retry when other issues occur in the source and destination databases parameter must be smaller than the value of the Retry Time for Failed Connection parameter.
Configure ETL	Specifies whether to configure the extract, transform, and load (ETL) feature. For more information, see What is ETL?. Valid values: Yes: configures the ETL feature. You can enter data processing statements in the code editor. For more information, see Configure ETL in a data migration or data synchronization task. No: does not configure the ETL feature.

In the lower part of the page, click Next: Configure Database and Table Fields. On the page that appears, set the primary key columns and distribution key columns of the tables that you want to synchronize to the destination AnalyticDB for PostgreSQL instance.
Click Next: Save Task Settings and Precheck in the lower part of the page.
You can move the pointer over Next: Save Task Settings and Precheck and click Preview OpenAPI parameters to view the parameter settings of the API operation that is called to configure the instance.
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, 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.
Wait until the success rate becomes 100%. Then, click Next: Purchase Instance.

On the Purchase Instance page, configure the Billing Method and Instance Class parameters for the data synchronization instance. The following table describes the parameters.

Section	Parameter	Description
New Instance Class	Billing Method	Subscription: You pay for the instance 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 charged on an hourly basis. The pay-as-you-go billing method is suitable for short-term use. If you no longer require a pay-as-you-go instance, you can release the pay-as-you-go instance to reduce costs.
	Resource Group	The resource group on which the instance is run. Default value: default resource group. For more information, see What is Resource Management?.
	Instance Class	DTS provides various synchronization specifications that provide different performance. The synchronization speed varies based on the synchronization specifications that you select. You can select a synchronization specification 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, one year, two years, three years, or five years. Note This parameter is available only if you select the Subscription billing method.

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