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

You can configure a data migration task in 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 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.
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.

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 select tables as the objects to be migrated and you need to edit tables (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 split the tables to be migrated, configure multiple tasks to migrate the tables, or configure a task to migrate the entire database. A single data migration task can migrate up to 10 databases. If you need to migrate more than 10 databases, we recommend that you split the tables to be migrated or configure multiple tasks to migrate the databases. Otherwise, the performance and stability of your data migration task may be compromised. If you need 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. 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. After full data migration is completed, you can set the retention period to more than 24 hours. Otherwise, DTS may fail to obtain the data logs and the task may fail. In extreme cases, data may be inconsistent or lost. 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 and performance. 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. 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 migrated must have clustered indexes that contain primary key columns. 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 completed, 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, 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 MySQL 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 completed, 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 statement
DML	INSERT, UPDATE, and DELETE
DDL	CREATE TABLE Note If a CREATE TABLE statement contains partitioning clauses, subpartitioning clauses, or functions, DTS does not synchronize the statement. ALTER TABLE ADD COLUMN and DROP COLUMN DROP TABLE CREATE INDEX and DROP INDEX Note Transactional DDL statements cannot be migrated.

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	sysadmin
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 a database account and grant permissions to the account, see the following topics:

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

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 want to migrate incremental data from multiple databases, repeat Steps 1 to 4 for each database.

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
```
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
```
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
```

Procedure

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, click DTS.. In the left-side navigation pane, click Data Migration.
In the top navigation bar, select the region where the data migration instance resides.

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 helps you create and run the data migration task.


Section	Parameter	Description
N/A	Task Name	DTS automatically generates a task name. We recommend that you specify an informative name to identify the task. You do not need to use a unique task name.
Source Database	Database Type	Select SQL Server.
	Access Method	Select User-Created Database in ECS Instance. 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 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.
	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 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 Cloud Instance.
	Instance Region	The region where 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 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	Enter the password of the database account.

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.
Warning
- If the source or destination database instance 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 database instance. If the source or destination database instance is a self-managed database hosted on Elastic Compute Service (ECS), DTS automatically adds the CIDR blocks of DTS servers to the security group rules of the ECS 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 that is deployed in data centers or provided by third-party cloud service providers, you must manually add the CIDR blocks of DTS servers to allow DTS to access the database.
- If the CIDR blocks of DTS servers are automatically or manually added to the whitelist of the database instance 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: enhance the security of your account and password, limit the ports that are exposed, authenticate API calls, regularly check the whitelist or ECS security group rules and forbid unauthorized CIDR blocks, or connect the database to DTS by using Express Connect, VPN Gateway, or Smart Access Gateway.
- After the DTS task is completed or released, we recommend that you manually detect and remove the added CIDR blocks from the whitelist of the database instance or ECS security group rules.

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. 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 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 specific 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. Disadvantages: 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. Disadvantages: Heap tables, tables without primary keys, compressed tables, and tables with computed columns are not supported.
DDL and DML Operations to Be Synchronized	The SQL operations to migrate at the instance level. For more information, see SQL operations that can be migrated. 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 icon to add the objects to the Selected Objects section. Note In this scenario, data migration is performed between heterogeneous databases. Therefore, the objects to be migrated are tables. Other objects such as views, triggers, and stored procedure 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 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, see SQL operations that can be migrated.

Advanced 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 range for failed connections. Valid values: 10 to 720. Unit: minutes. Default value: 720. 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 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 value that is set later 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.

Specify the primary key columns and distribution keys of the tables that you want to migrate to the AnalyticDB for PostgreSQL instance.
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, you can click the 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.
Wait until the Success Rate becomes 100%. Then, click Next: Purchase Instance.

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.

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