Data Transmission Service:Migrate incremental data from a self-managed SQL Server database to an ApsaraDB RDS for SQL Server instance

Prerequisites

• The version of the self-managed SQL Server database is 2008, 2008 R2, 2012, 2014, 2016, or 2017.

  Note

  • If a primary/secondary switchover is performed in an SQL Server cluster or Always On availability group (AOAG), the log serial numbers of the primary database and the secondary database become inconsistent. In this case, DTS considers that the logs of the source database are discontinuous, and the migration task fails. Therefore, you cannot use an SQL Server cluster or an SQL Server AOAG as the source database.

  • If you migrate data between different versions of databases, make sure that the database versions are compatible.

• The tables to be migrated from the self-managed SQL Server database have primary keys or UNIQUE NOT NULL indexes.

• The available storage space of the ApsaraDB RDS for SQL Server instance is larger than the total size of the data in the self-managed SQL Server database.

Usage notes

• DTS uses read and write resources of the source and destination databases during full data migration. This may increase the loads of the database servers. If the database performance is unfavorable, the specification is low, or the data volume is large, database services may become unavailable. For example, DTS occupies a large amount of read and write resources in the following cases: a large number of slow SQL queries are performed on the source database, the tables have no primary keys, or a deadlock occurs in the destination 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. For example, you can migrate data when the CPU utilization of the source and destination databases is less than 30%.

• To ensure that the incremental data migration task runs as expected, do not frequently back up the source database. We recommend that you retain log files for more than three days. Otherwise, you cannot retrieve log files after they are truncated.

• To ensure that the latency 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 in the source table name_dts_mysql_heartbeat format.

• DTS automatically creates a destination database in the ApsaraDB RDS for SQL Server instance. However, if the name of the source database does not conform to the naming conventions of ApsaraDB RDS, you must create a database in the ApsaraDB RDS for SQL Server instance before you configure the data migration task.

  Note

  For more information about the database naming conventions and how to create a database in ApsaraDB RDS for SQL Server, see Create a database on an ApsaraDB RDS for SQL Server instance.

• If the destination database contains an enabled trigger or foreign key, the migration task fails.

• If a data migration task fails and stops, DTS automatically resumes the task. Before you switch your workloads to the destination instance, stop or release the data migration task. Otherwise, the data in the source database overwrites the data in the destination instance after the task is resumed.

Limits

• DTS does not migrate 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 migrate data of the SQL_VARIANT type.

• DTS does not migrate tables that contain computed columns.

• A single data migration task can migrate incremental data from only one database. To migrate incremental data from multiple databases, you must create a data migration task for each database.

Migration types

• Schema migration

  DTS migrates the schemas of objects to the destination database. DTS supports schema migration for the following types of objects: table, view, trigger, synonym, SQL stored procedure, SQL function, plan guide, user-defined type, rule, default, and sequence.

• Full data migration

  DTS migrates historical data of objects from the self-managed SQL Server database to the destination database.

• Incremental data migration

  After full data migration is complete, DTS migrates incremental data from the self-managed SQL Server database to the destination database.

SQL operations that can be incrementally migrated

• INSERT, UPDATE, and DELETE

  Note

  If an UPDATE operation updates only the large fields, DTS does not migrate the operation.

• CREATE TABLE

  Note

  If a CREATE TABLE statement contains partitioning clauses, subpartitioning clauses, or functions, DTS does not migrate the operation.

• ALTER TABLE, including only ADD COLUMN, DROP COLUMN, and RENAME COLUMN

• DROP TABLE

• RENAME TABLE, TRUNCATE TABLE, and CREATE INDEX

Billing rules

Permissions required for database accounts

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

• ApsaraDB RDS for SQL Server instance: Create an account for an ApsaraDB RDS for SQL Server instance.

Process of incremental data migration

To prevent data migration failures caused by dependencies among objects, DTS migrates the schemas and data from the source SQL Server database in the following order:

1. Migrate the schemas of tables, views, synonyms, user-defined types, rules, defaults, and plan guides.

2. Perform full data migration.

3. Migrate the schemas of SQL stored procedures, SQL functions, triggers, and foreign keys.

4. Perform incremental data migration.

   Note

   During incremental data migration, we recommend that you do not perform data definition language (DDL) operations on the source objects. Otherwise, the objects may fail to be migrated.

Before you begin

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

1. 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

   Parameter:

   <database_name>: the name of the source database.

   Example:

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

2. 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

3. 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

4. Create a clustered index for each source table. For more information, see Create Clustered Indexes.

Procedure

1. Log on to the DTS console.

   Note

   If you are redirected to the Data Management (DMS) console, you can click the icon in the to go to the previous version of the DTS console.

2. In the left-side navigation pane, click Data Migration.

3. In the upper part of the Migration Tasks page, select the region in which the RDS instance resides.

4. In the upper-right corner of the page, click Create Migration Task.

5. 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 specify a unique task name.
   Source Database	Instance Type	The access method of the source database. In this example, User-Created Database with Public IP Address is selected. Note If you select other instance types, you must deploy the network environment for the self-managed database. For more information, see Preparation overview.
   	Instance Region	The region in which the source database resides. If you select User-Created Database with Public IP Address as the instance type, you do not need to set the Instance Region parameter. Note If a whitelist is configured for the self-managed SQL Server database, you must add the CIDR blocks of DTS servers to the whitelist of the database. You can click Get IP Address Segment of DTS next to the Instance Region field to obtain the CIDR blocks of DTS servers.
   	Database Type	The type of the source database. Select SQL Server.
   	Hostname or IP Address	The endpoint that is used to connect to the self-managed SQL Server database. In this example, the public IP address is specified.
   	Port Number	The service port number of the self-managed SQL Server database. Default value: 1433. Note In this example, the service port of the self-managed SQL Server database must be accessible over the Internet.
   	Database Account	The account of the self-managed SQL Server database. For more information about the permissions that are required for the account, see Permissions required for database accounts.
   	Database Password	The password of the database account. Note After you specify the information about the source database, you can click Test Connectivity next to Database Password to check whether the information is valid. If the information is valid, the Passed message appears. If the Failed message appears, click Check next to Failed. Then, modify the information based on the check results.
   Destination Database	Instance Type	The type of the destination database. Select RDS Instance.
   	Instance Region	The region in which the destination ApsaraDB RDS for SQL Server instance resides.
   	RDS Instance ID	The ID of the ApsaraDB RDS for SQL Server instance.
   	Database Account	The database account of the destination ApsaraDB RDS for SQL Server instance. For more information about the permissions that are required for the account, see Permissions required for database accounts.
   	Database Password	The password of the database account. Note After you specify the information about the RDS instance, you can click Test Connectivity next to Database Password to check whether the information is valid. If the information is valid, the Passed message appears. If the Failed message appears, click Check next to Failed. Then, modify the information based on the check results.

6. In the lower-right corner of the page, click Set Whitelist and Next.

   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 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 username 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.

7. Select the objects to be migrated and the migration types.

   Setting	Description
   Select the 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. In this example, the three migration types are selected. Note If Incremental Data Migration is not selected, do not write data to the self-managed SQL Server database during full data migration. This ensures data consistency between the source and destination databases.
   Select the objects to be migrated	Select one or more objects from the Available section and click the icon to add the objects to the Selected section. Note A single data migration task can migrate incremental data from only one database. To migrate incremental data from multiple databases, you must create a data migration task for each database. You can select columns, tables, or databases as the objects to be migrated. By default, after an object is migrated to the destination database, the name of the object remains unchanged. You can use the object name mapping feature to rename the objects that are migrated to the destination database. For more information, see Object name mapping. 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.
   Specify whether to rename objects	You can use the object name mapping feature to rename the objects that are migrated to the destination instance. For more information, see Object name mapping.
   Specify the retry time range for failed connections to the self-managed SQL Server database or ApsaraDB RDS for SQL Server instance	By default, if DTS fails to connect to the source and destination databases, DTS retries within the following 12 hours. You can specify the retry time range based on your business requirements. If DTS is reconnected to the source and destination databases within the specified time range, DTS resumes the data migration task. Otherwise, the data migration task fails. Note Within the time range in which DTS attempts to reconnect to the source and destination databases, 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 the earliest opportunity after the source and destination databases are released.

8. Click Precheck.

   Note

   • A precheck is performed before the migration task starts. The migration task only starts after the precheck succeeds.

   • If the precheck fails, click the icon next to each failed check item to view the related details. Fix the issues as instructed and run the precheck again.

9. Click Next.

10. In the Confirm Settings dialog box, configure the Channel Specification parameter. Then, read and select Data Transmission Service (Pay-as-you-go) Service Terms.

11. Click Buy and Start to start the data migration task.

    • Full data migration

      Do not manually stop a full data migration task. If you manually stop a full data migration task, the data that is migrated to the RDS instance may be incomplete. You can wait until the data migration task automatically stops.

    • Incremental data migration

      An incremental data migration task does not automatically stop. You must manually stop the task.

      Note

      We recommend that you manually stop an incremental data migration task at an appropriate point in time. For example, you can stop the task during off-peak hours or before you switch your workloads over to the ApsaraDB RDS for MySQL instance.

      1. Wait until Incremental Data Migration and The data migration task is not delayed are displayed in the progress bar of the data migration task. Then, stop writing data to the source database for a few minutes. The latency of incremental data migration may be displayed in the progress bar.

      2. Wait until the status of Incremental Data Migration changes to The data migration task is not delayed again. Then, manually stop the migration task.

12. Switch your workloads to the ApsaraDB RDS for SQL Server instance.

What to do next

The database accounts that are used for data migration have the read and write permissions. After data migration is complete, you must delete the accounts of both the self-managed SQL Server database and the ApsaraDB RDS for SQL Server instance to ensure security.