This topic describes how to use Data Transmission Service (DTS) to migrate data between ApsaraDB RDS for SQL Server instances. DTS supports schema migration, full data migration, and incremental data migration. When you configure a data migration task, you can select all of the supported migration methods to ensure business continuity.

Prerequisites

  • A source RDS instance and a destination RDS instance are created. For more information, see Create an ApsaraDB RDS for SQL Server instance.
    Note
    • For compatibility purposes, we recommend that the database engine version of the destination RDS instance be the same as or later than the database engine version of the source RDS instance.
    • If the database engine version of the destination RDS instance is earlier than the database engine version of the source RDS instance, database compatibility issues may occur.
  • The storage capacity of the destination RDS instance is larger than the storage that is occupied by the source RDS instance.

Usage notes

  • The data migration does not affect the data of the source RDS instance. During data migration, DTS reads the data of the source RDS instance and replicates the data to the destination RDS instance. DTS does not delete the data of the source RDS instance. For more information, see How DTS works in data migration mode.
  • 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%.
  • The tables to be migrated in the source database must have PRIMARY KEY or UNIQUE constraints and all fields must be unique. Otherwise, the destination database may contain duplicate data records.
  • To ensure data consistency, we recommend that you do not write data to the source RDS instance during full data migration.
  • If a data migration task fails, DTS automatically resumes the task. Before you switch your workloads over to the destination RDS instance, you must stop or release the data migration task. Otherwise, the data of the source RDS instance overwrites the data of the destination RDS instance if the data migration task is running or resumed.
  • DTS automatically creates databases on the destination RDS instance. If the name of a database that you want to replicate from the source RDS instance is invalid, you must log on to the destination RDS instance and create a database for the database that you want to replicate before you configure the migration task.
    Note For more information about how to create a database and the database naming conventions, see Create accounts and databases for an ApsaraDB RDS instance that runs SQL Server 2017 EE.

Billing

Migration type Task 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 the specified objects from the source ApsaraDB RDS instance to the destination ApsaraDB RDS instance.

  • Full data migration

    DTS migrates all historical data of the specified objects from the source ApsaraDB RDS instance to the destination ApsaraDB RDS instance.

  • Incremental data migration

    After full data migration is complete, DTS synchronizes incremental data from the source ApsaraDB RDS instance to the destination ApsaraDB RDS instance. Incremental data migration allows you to ensure service continuity when you migrate data between ApsaraDB RDS instances.

SQL operations that can be synchronized during incremental data migration

Operation type SQL statement
DML INSERT, UPDATE, and DELETE
Note If an UPDATE operation updates only large fields, DTS does not synchronize the operation.
DDL
  • ALTER TABLE, including only ADD COLUMN, DROP COLUMN, and RENAME COLUMN
  • CREATE TABLE and CREATE INDEX
    Note If a CREATE TABLE operation creates a partitioned table or a table that contains functions, DTS does not synchronize the operation.
  • DROP TABLE
  • RENAME TABLE
  • TRUNCATE TABLE

Permissions required for database accounts

Instance Schema migration Full data migration Incremental data migration
Source RDS instance SELECT permission SELECT permission Owner permissions on the objects to be migrated
Note A privileged account has the required permissions.
Destination RDS instance Read and write permissions Read and write permissions Read and write permissions

For more information about how to create a database account and grant permissions to the account, see Create an account for an RDS SQL Server instancy and Create a database on an ApsaraDB RDS for SQL Server instance.

Procedure

  1. 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.
  2. In the top navigation bar, select the region where the data migration instance resides.
    Select a region
  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
    None 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 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 source database.
    Database Type Select SQL Server.
    Access Method Select Alibaba Cloud Instance.
    Instance Region Select the region of the source RDS instance.
    Replicate Data Across Alibaba Cloud Accounts Specify whether to synchronize data across Alibaba Cloud accounts. In this example, No is selected.
    • No: Data is migrated within the same Alibaba Cloud account.
    • Yes: Data is migrated across Alibaba Cloud accounts.
      If you select Yes, you must configure the following parameters:
      • Alibaba Cloud Account: Enter the Alibaba Cloud account that owns the source RDS instance.
        Note To obtain the ID of the Alibaba Cloud account that owns the source RDS instance, you can log on to the Account Center console by using this account. The account ID is displayed on the Security Settings page.
      • RAM Role Name: Enter the role name configured for the Alibaba Cloud account that owns the source RDS instance. For more information, see Configure RAM authorization for cross-account data migration and synchronization.
    RDS Instance ID Select the ID of the source RDS instance.
    Database Account Enter the username of the account that is used to log on to the database of the source RDS instance. For information about account permissions, see Permissions required for database accounts.
    Database Password Enter the password of the account that is used to log on to the database of the source RDS instance.
    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 source database.
    Database Type Select SQL Server.
    Access Method Select Alibaba Cloud Instance.
    Instance Region Select the region in which the destination RDS instance resides.
    Instance ID Select the ID of the destination RDS instance.
    Database Account Enter the username of the account that is used to log on to the database of the destination RDS instance. For information about account permissions, see Permissions required for database accounts.
    Database Password Enter the password of the account that is used to log on to the database of the destination RDS instance.
  4. In the lower part of the page, 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, or is a self-managed database hosted on Elastic Compute Service (ECS), DTS automatically adds the CIDR blocks of DTS servers to the whitelist of the database instance or ECS security group rules. 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 on data centers or is from other 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, 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.
    • 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.
      Select Objects

      Select one or more objects from the Source Objects section and click the Rightwards arrow 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, and stored procedures 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 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.
      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 synchronized during incremental data migration.
    • 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.
      Configure ETL Specify whether to configure the extract, transform, and load (ETL) feature. For more information, see What is ETL?What is ETL?. Valid values:
  6. In the lower-right corner 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 the Info icon icon next to each failed item to view details.
      • After you troubleshoot the issues based on the details, run a precheck again.
      • If you do not need to troubleshoot the issues, ignore failed items and run a precheck again.
  7. Wait until the Success Rate becomes 100%. Then, click Next: Purchase Instance.
  8. In the Purchase Instance step, 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.

  9. Read and select Data Transmission Service (Pay-as-you-go) Service Terms.
  10. Click Buy and Start. In the message that appears, click OK.
    The migration task starts. You can view the progress of the migration task on the Data Migration page.