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

This topic describes how to migrate 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 data with ease and analyze data in real time.

Prerequisites

The new DTS console is used. 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 ApsaraDB RDS for SQL Server instance meets one of the following conditions, we recommend that you split the migration 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 migration, DTS migrates foreign keys from the source database to the destination database.
During full data migration and incremental data migration, DTS temporarily disables the constraint check and cascade operations on foreign keys at the session level. If you perform the cascade and delete operations on the source database during data migration, data inconsistency may occur.

Category	Description
Limits on the source database	Bandwidth requirements: The server to which the source database belongs must have sufficient outbound bandwidth. Otherwise, the data migration speed decreases. 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 select tables as the objects to be migrated and you need to edit the tables in the destination database, such as renaming tables or columns, up to 1,000 tables can be migrated in a single data migration task. If you run a task to migrate more than 1,000 tables, a request error occurs. In this case, we recommend that you configure multiple tasks to migrate the tables in batches, or configure a task to migrate the entire database. You can run a single data migration task to migrate up to 10 databases. If you want to migrate more than 10 databases, we recommend that you configure multiple tasks to migrate the databases in batches. Otherwise, the performance and stability of your data migration task may be compromised. If you need to migrate incremental data, 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 physical backup must be performed. If you perform only incremental data migration, the data logs of the source database must be stored for more than 24 hours. If you perform both full data migration and incremental data migration, 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 full data migration 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 the change data capture (CDC) feature needs to be enabled for the tables that you want to migrate from the source database, the following conditions must be met. 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. DTS uses the fn_log function to obtain logs of the source database. However, this function has performance bottlenecks. We recommend that you do not clear the logs of the source database before the task is complete. Otherwise, the task may fail. Limits on operations to be performed on the source database: During schema migration and full data migration, do not perform 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 inconsistency may occur 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. If the source database is a read-only instance, you cannot migrate DDL operations. In hybrid log-based parsing mode, you cannot perform multiple operations to add columns to or remove columns from the source database within 10 minutes. For example, if you execute the following SQL statements within 10 minutes, an error is reported for the task. `ALTER TABLE test_table DROP COLUMN Flag; ALTER TABLE test_table ADD Remark nvarchar(50) not null default('');`
Other limits	DTS does not migrate data of the following types: TIMESTAMP, CURSOR, ROWVERSION, HIERACHYID, SQL_VARIANT, SPATIAL GEOMETRY, SPATIAL GEOGRAPHY, and TABLE. If you select tables as the objects to be migrated, you can modify the mapping relation between columns. If column mapping is used for non-full table migration or if the schemas of the source and destination tables are inconsistent, the data in the columns of the source database that are not contained in the destination database will be lost. The table cannot be an append-optimized (AO) table. If you set the SQL Server Incremental Synchronization Mode parameter to Incremental Synchronization Based on Logs of Source Database in the Configure Objects and Advanced Settings step, the tables to be migrated must have clustered indexes that contain primary key columns. In addition, the tables to be migrated cannot be heap tables, compressed tables, tables without primary keys, or tables with computed columns. Ignore the preceding limits if the hybrid log-based parsing mode is used. Note For more information about how to view table information, see the 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? section of the "FAQ" topic. In Incremental Synchronization Based on Logs of Source Database 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 in the source database to ensure that the latency of data migration is accurate. In 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 and enables CDC for the source database and specific tables. We recommend that you set the maximum number of records per second to 1,000 for the tables for which CDC is enabled in the source database. 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 the read and write resources of the source and destination databases. This may increase the loads on 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 size of used 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 meet 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 columns of the FLOAT data type to 38 digits and the precision for columns of 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 database, you must stop or release the failed tasks. You can also execute the `REVOKE` statement to revoke the write permissions from the accounts that are used by DTS to access the destination database. Otherwise, the data in the source database overwrites the data in the destination database after a failed task is resumed. If the data migration task involves incremental data migration, DTS does not allow you to perform the reindexing operation. If you perform the reindexing operation, the data migration task may fail, or even data loss may occur. Note DTS cannot migrate DDL operations related to the primary key of a table for which CDC is enabled. If the number of CDC-enabled tables to be migrated in a single migration task exceeds 1,000, the precheck fails.

Billing

Migration type	Instance configuration fee	Internet traffic fee
Schema migration and full data migration	Free of charge.	Charged only when data is migrated from Alibaba Cloud over the Internet. For more information, see Billing overview.
Incremental data migration	Charged. For more information, see Billing overview.

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 mappings on your business. For more information, see Data type mappings between heterogeneous databases.
Full data migration
DTS migrates the existing 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 the services of self-managed applications during data migration.

SQL operations that can be incrementally migrated

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 migrate the operation. ALTER TABLE ADD COLUMN and DROP COLUMN DROP TABLE CREATE INDEX and DROP INDEX Note DTS does not migrate DDL operations that contain user-defined types. DTS does not migrate transactional DDL operations.

Permissions required for database accounts

Database	Schema migration	Full data migration	Incremental data migration
Self-managed SQL Server database	SELECT permission	SELECT permission	sysadmin
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.

For more information about how to create a database account and grant permissions to the database account, see the following topics:

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

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.

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

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

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 back up the log entries of 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 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
- Operations may vary based on the mode and layout of the DMS console. For more information, see Simple mode and Customize the layout and style of the DMS console.
- You can also go to the Data Migration Tasks page of the new DTS console.
From the drop-down list next to Data Migration Tasks, select the region in which the data migration instance resides.
Note If you use the new DTS console, you must select the region in which the data migration instance resides in the upper-left corner.

Click Create Task. In the Create Task wizard, configure the source and destination databases.

Warning

After you configure the source and destination databases, we recommend that you read the limits that are displayed in the upper part of the page. Otherwise, the task may fail or data inconsistency may occur.

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. 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.
	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 information about the permissions that are required for the account, see Permissions required for database accounts.
	Database Password	The password of the database account.

If an IP address whitelist is configured for your self-managed database, add the CIDR blocks of DTS servers to the IP address whitelist. Then, click Test Connectivity and Proceed.
Warning
If the public CIDR blocks of DTS servers are automatically or manually added to the IP address whitelist of a database instance or to the security group rules of an ECS instance, 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 account and password, limiting the ports that are exposed, authenticating API calls, regularly checking the IP address whitelist or ECS security group rules and forbidding unauthorized CIDR blocks, and connecting the database to DTS by using Express Connect, VPN Gateway, or Smart Access Gateway.

Configure the objects to be migrated and advanced settings.

Parameter	Description
Migration Types	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 you do not select Incremental Data Migration, we recommend that you do not write data to the source database during data migration. This ensures data consistency between the source and destination databases.
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 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 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 the following potential risks: If the source and destination databases have the same schemas, DTS does not migrate data records that have the same primary key values as data records in the destination database. If the source and destination databases have different schemas, only specific columns are migrated or the data migration task fails. Proceed with caution.
SQL Server Incremental Synchronization Mode	Log-based Parsing for Non-heap Tables and CDC-based Incremental Synchronization for Heap Tables: Benefits: Supports heap tables, tables without primary keys, compressed tables, and tables with computed columns. Provides higher stability and a variety of complete DDL statements. Limits: DTS creates the trigger named dts_cdc_sync_ddl, the heartbeat table named dts_sync_progress, and the DDL storage table named dts_cdc_ddl_history in the source database, and enables change data capture (CDC) for the source database and specific tables. You cannot execute the SELECT INTO statement on a table for which CDC is enabled in the source database. You cannot manually delete triggers that are created by DTS in the source database. Incremental Synchronization Based on Logs of Source Database: Benefits: Does not modify the settings of the source database. Limits: 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 incrementally migrated section of this topic. 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 incrementally migrate.
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 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.
Selected Objects	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 Batch Edit 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. To specify WHERE conditions to filter data, right-click an object in the Selected Objects section. In the dialog box that appears, specify the conditions. For more information about how to specify the conditions, see Set filter conditions. 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 migrate. For more information, see the SQL operations that can be incrementally migrated section of this topic.

Click Next: Advanced Settings to configure advanced settings.

Parameter	Description
Set Alerts	Specifies whether to configure alerting for the data migration task. If the task fails or the migration latency exceeds the specified threshold, the alert contacts will receive notifications. Valid values: No: does not configure alerting. Yes: configures alerting. If you select Yes, you must also specify the alert threshold and alert contacts. For more information, see Configure monitoring and alerting.
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 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 DDL or DML operations fail to be performed after the data migration task is started, DTS immediately retries the operations within the retry 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 retry time range, DTS resumes the data migration task. Otherwise, the data migration 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 Connections parameter.
Configure ETL	Specifies whether to enable 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.

Specify the primary key columns and distribution key columns of the tables that you want to migrate to the destination AnalyticDB for PostgreSQL instance.
In the lower part of the page, click Next: Save Task Settings and Precheck.
You can move the pointer over Next: Save Task Settings and Precheck and click Preview OpenAPI parameters to view the parameters to be specified when you call the relevant API operation to configure the DTS 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, click View Details next to each failed item. After you troubleshoot the issues based on the error message, you can run a precheck again.
- If an alert is triggered for an item during the precheck:
  If the alert item cannot be ignored, click View Details next to the failed item and troubleshoot the issues. Then, run a precheck again.
  If the 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 Instance Class parameter for the data migration instance. The following table describes the parameters.

Section	Parameter	Description
New Instance Class	Resource Group	The resource group to which the data migration instance belongs. Default value: default resource group. For more information, see What is Resource Management?
New Instance Class	Instance Class	DTS provides 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.

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