Data Transmission Service:Migrate 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 supported by DTS. For more information, see Overview of data migration scenarios.
• The destination ApsaraDB RDS for SQL Server instance is created. For more information, see Create an ApsaraDB RDS for SQL Server instance.
• 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.
• 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.
  • 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.
  • The logs of a database in the source ApsaraDB RDS for SQL Server instance involve heap tables, tables without primary keys, compressed tables, or tables with computed columns. You can execute the following SQL statements to check whether the source database contains these tables.
    1. Execute the following SQL statement to check for heap tables:

       SELECT s.name AS schema_name, t.name AS table_name FROM sys.schemas s INNER JOIN sys.tables t ON s.schema_id = t.schema_id AND t.type = 'U' AND s.name NOT IN ('cdc', 'sys') AND t.name NOT IN ('systranschemas') AND t.object_id IN (SELECT object_id FROM sys.indexes WHERE index_id = 0);

    2. Execute the following SQL statement to check for tables without primary keys:

       SELECT s.name AS schema_name, t.name AS table_name FROM sys.schemas s INNER JOIN sys.tables t ON s.schema_id = t.schema_id AND t.type = 'U' AND s.name NOT IN ('cdc', 'sys') AND t.name NOT IN ('systranschemas') AND t.object_id NOT IN (SELECT parent_object_id FROM sys.objects WHERE type = 'PK');

    3. Execute the following SQL statement to check for primary key columns contained in clustered index columns:

       SELECT s.name AS schema_name, t.name AS table_name FROM sys.schemas s INNER JOIN sys.tables t ON s.schema_id= t.schema_id WHERE t.type= 'U' AND s.name NOT IN('cdc', 'sys')  AND t.name NOT IN('systranschemas')  AND t.object_id IN (SELECT pk_columns.object_id AS object_id FROM (select sic.object_id object_id, sic.column_id FROM sys.index_columns sic, sys.indexes sis WHERE sic.object_id= sis.object_id AND sic.index_id= sis.index_id AND sis.is_primary_key= 'true') pk_columns LEFT JOIN (SELECT sic.object_id object_id, sic.column_id FROM sys.index_columns sic, sys.indexes sis WHERE sic.object_id= sis.object_id AND sic.index_id= sis.index_id AND sis.index_id= 1) cluster_colums ON pk_columns.object_id= cluster_colums.object_id WHERE pk_columns.column_id != cluster_colums.column_id);

    4. Execute the following SQL statement to check for compressed tables:

       SELECT s.name AS schema_name, t.name AS table_name FROM sys.objects t, sys.schemas s, sys.partitions p WHERE s.schema_id = t.schema_id AND t.type = 'U' AND s.name NOT IN ('cdc', 'sys') AND t.name NOT IN ('systranschemas') AND t.object_id = p.object_id AND p.data_compression != 0;

    5. Execute the following SQL statement to check for tables with computed columns:

       SELECT s.name AS schema_name, t.name AS table_name FROM sys.schemas s INNER JOIN sys.tables t ON s.schema_id = t.schema_id AND t.type = 'U' AND s.name NOT IN ('cdc', 'sys') AND t.name NOT IN ('systranschemas') AND t.object_id IN (SELECT object_id FROM sys.columns WHERE is_computed = 1);

Usage notes

Billing

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: table, view, trigger, synonym, SQL stored procedure, SQL function, plan guide, user-defined type, rule, default, and sequence.
  • 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.
• Full data migration

  DTS migrates the historical 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 you to ensure service continuity when you migrate data between self-managed databases.

SQL operations that can be migrated during incremental data migration

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 RDS SQL Server instancy and Modify the permissions of a standard account on an ApsaraDB RDS for SQL Server instance

Data migration process

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.

Preparations

1. Execute the following statement 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

   Parameters:

   <database_name>: the name of the source database.

   Example:

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

2. Execute the following statement to create a logical backup for the source database. Skip this step if you have already created a logical backup.

   BACKUP DATABASE <database_name> TO DISK='<physical_backup_device_name>';
   GO

   Parameters:
   • <database_name>: the name of the source database.
   • <physical_backup_device_name>: the storage path and file name of the backup file.
   Example:

   BACKUP DATABASE mytestdata TO DISK='D:\backup\dbdata.bak';
   GO

3. Execute the following statement to 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

1. 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 You can also configure the settings by using the new DTS console.
2. From the drop-down list to the right of Data Migration Tasks, select the region in which your data migration instance resides.
   Note If you use the new DTS console, select the region in which your data migration instance resides in the upper-left corner.
3. 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	The name of the task. DTS automatically generates a task name. We recommend that you specify a descriptive name to identify the task. You do not need to specify a unique task name.
   Source Database	Select Instance	The instance that you want to use. You can choose whether to use an existing instance based on your business requirements. If you use an existing instance, DTS automatically applies the parameter settings of the instance. If you do not use an existing instance, you must set parameters for the database.
   	Database Type	The type of the source database. Select SQL Server.
   	Access Method	The access method of the source database. Select Public IP Address. 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.
   	Hostname or IP address	The endpoint that is used to access to the self-managed SQL Server database. In this example, a public IP address is used.
   	Port Number	The service port number of the self-managed SQL Server database. The default port number is 1433.
   	Database Account	The database 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	The password of the database account.
   Destination Database	Select Instance	The instance that you want to use. You can choose whether to use an existing instance based on your business requirements. If you use an existing instance, DTS automatically applies the parameter settings of the instance. If you do not use an existing instance, you must set parameters for the database.
   	Database Type	The type of the destination database. Select SQL Server.
   	Access Method	The access method of the destination database. Select Alibaba Cloud Instance.
   	Instance Region	The region in which the destination ApsaraDB RDS for SQL Server instance resides.
   	RDS Instance ID	The ID of the destination 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.

4. If a whitelist is configured for your self-managed database, add the CIDR blocks of DTS servers to the whitelist. Then, click Test Connectivity and Proceed.
   Warning

   • 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. 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 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.
   • If the CIDR blocks of DTS servers are automatically or manually added to the whitelist of the database, Alibaba Cloud 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: 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.
   • After the DTS task is complete or released, we recommend that you manually detect and remove the added CIDR blocks from the whitelist of the database, Alibaba Cloud database instance, or ECS security group rules.
5. Select objects for the task and configure advanced 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 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 identical table names and the tables in the destination database cannot be deleted or renamed. For more information, see Map object names. Ignore Errors and Proceed: skips the precheck for identical table names in the source and destination databases. Warning If you select Ignore Errors and Proceed, data inconsistency may occur, and your business may be exposed to potential risks. If the source and destination databases have the same schema, 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: 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 You can select columns, tables, or schemas as the objects to be migrated. If you select tables or columns as the objects to be migrated, DTS does not migrate other objects such as views, triggers, or stored procedures 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 the procedure, see Use SQL conditions to filter data. 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 SQL operations that can be migrated during incremental data migration.

6. Click Next: Advanced Settings to configure advanced settings.

   Parameter	Description
   Set Alerts	Specifies 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. Valid values: No: does not set alerts. Yes: sets alerts. If you select Yes, you must also set the alert threshold and alert contacts.
   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 retry 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.
   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.

7. 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, click View Details next to each failed item. After you analyze the causes based on the check result, troubleshoot the issues. Then, run a precheck again.
   • If an alert is triggered for an item during the precheck, click Confirm Alert Details next to the item and analyze the causes.
     • You can troubleshoot the issues based on the causes and run a precheck again.
     • If you do not need to troubleshoot the issues, 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.
8. Wait until the Success Rate becomes 100%. Then, click Next: Purchase Instance.
9. On the Purchase Instance page, specify the Instance Class parameter for the data migration instance. The following table describes the parameter.

   Section	Parameter	Description
   New Instance Class	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.

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