The Data Transmission Service (DTS) supports migration between RDS for SQL Server instances.
Prerequisites
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You have created source and destination RDS for SQL Server instances. For supported versions, see Migration overview. To create an instance, see Create an RDS for SQL Server instance.
Important-
Incremental data migration is not supported if the source RDS for SQL Server version is 2008 or 2008 R2.
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When the SQL Server incremental sync mode is set to Use log parsing for non-heap tables and CDC for heap tables, enabling hybrid log parsing mode, the following source databases are supported:
Enterprise or Enterprise Evaluation Edition: 2012, 2014, 2016, 2019, or 2022.
Standard Edition: 2016, 2019, or 2022.
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The storage space of the destination RDS for SQL Server instance must be larger than the storage space used by the source RDS for SQL Server instance.
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If any of the following conditions apply to the source instance, you must split the migration into multiple tasks.
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The number of databases exceeds 10.
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Log backups are performed on a single database more than once per hour.
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DDL operations are performed on a single database more than 100 times per hour.
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The log volume of a single database exceeds 20 MB/s.
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Change Data Capture (CDC) needs to be enabled for more than 1,000 tables.
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Important notes
DTS does not migrate foreign keys from the source database to the destination database. Therefore, cascade and delete operations in the source database are not migrated to the destination database.
Type | Description |
Source database limits |
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Other limits |
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Special cases |
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Billing
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Migration type |
Instance configuration fee |
Internet traffic fee |
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Schema migration and full data migration |
Free of charge. |
When the Access Method parameter of the destination database is set to Public IP Address, you are charged for Internet traffic. For more information, see Billing overview. |
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Incremental data migration |
Charged. For more information, see Billing overview. |
Migration types
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Schema migration
DTS migrates the schema definitions of selected objects from the source database to the destination database.
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Full migration
DTS migrates all historical data of selected objects from the source database to the destination database.
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Incremental migration
After a full migration, DTS migrates incremental updates from the source database to the destination database. This process enables smooth data migration without application downtime.
SQL operations supported for incremental migration
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Operation type |
SQL statements |
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DML |
INSERT, UPDATE, DELETE Note
UPDATE statements that modify only large object columns are not supported. |
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DDL |
Note
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Database account permissions
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Database |
Schema migration |
Full migration |
Incremental migration |
How to create and authorize a database account |
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Source instance |
Read permission |
Read permission |
Owner permission on the objects to migrate. |
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target instance |
Read and write permission |
Read and write permission |
Read and write permission. |
Procedure
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Navigate to the migration task list page for the destination region using one of the following methods.
From the DTS console
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Log on to the Data Transmission Service (DTS) console.
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In the navigation pane on the left, click Data Migration.
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In the upper-left corner of the page, select the region where the migration instance is located.
From the DMS console
NoteThe actual operations may vary based on the mode and layout of the DMS console. For more information, see Simple mode console and Customize the layout and style of the DMS console.
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Log on to the Data Management (DMS) console.
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In the top menu bar, choose .
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To the right of Data Migration Tasks, select the region where the migration instance is located.
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Click Create Task to navigate to the task configuration page.
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Optional: In the upper-right corner of the page, click New Configuration Page.
Note-
If you are already on the new configuration page (the button in the upper-right corner is Back to Previous Version), you can skip this step.
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The parameters on the new and old configuration pages are different. We recommend that you use the new configuration page.
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Configure the source and destination databases.
Category
Configuration
Description
None
Task Name
DTS automatically generates a task name. We recommend that you specify a descriptive name for easy identification. The name does not need to be unique.
Source Database
Select Existing Connection
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To use a database instance that has been added to the system (created or saved), select the desired database instance from the drop-down list. The database information below will be automatically configured.
NoteIn the DMS console, this parameter is named Select a DMS database instance..
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If you have not registered the database instance with the system, or do not need to use a registered instance, manually configure the database information below.
Database Type
Select SQL Server.
Connection Type
Select Cloud instance.
Instance Region
Select the region where the source RDS for SQL Server instance resides.
Cross-account
This example migrates within the same Alibaba Cloud account. Select Not cross-account.
RDS instance ID
Select the source RDS for SQL Server instance ID.
Database Account
Enter the database account for the source RDS for SQL Server instance. For required permissions, see Database account permissions.
Database Password
Enter the password for the database account.
Encryption
Select Non-encrypted or SSL-encrypted based on your environment.
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If SSL encryption is disabled on the source database, select Non-encrypted.
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If SSL encryption is enabled on the source database, select SSL-encrypted. DTS trusts the server certificate by default.
Destination Database
Select Existing Connection
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To use a database instance that has been added to the system (created or saved), select the desired database instance from the drop-down list. The database information below will be automatically configured.
NoteIn the DMS console, this parameter is named Select a DMS database instance..
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If you have not registered the database instance with the system, or do not need to use a registered instance, manually configure the database information below.
Database Type
Select SQL Server.
Connection Type
Select Cloud instance.
Instance Region
Select the region where the destination RDS for SQL Server instance resides.
Instance ID
Select the destination RDS for SQL Server instance ID.
Database Account
Enter the database account for the destination RDS for SQL Server instance. For required permissions, see Database account permissions.
Database Password
Enter the password for the database account.
Encryption
Select Non-encrypted or SSL-encrypted based on your environment.
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If SSL encryption is disabled on the destination database, select Non-encrypted.
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If SSL encryption is enabled on the destination database, select SSL-encrypted. DTS trusts the server certificate by default.
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After you complete the configuration, click Test Connectivity and Proceed at the bottom of the page.
Note-
Ensure that the IP address segment of the DTS service is automatically or manually added to the security settings of the source and destination databases to allow access from DTS servers. For more information, see Add DTS server IP addresses to a whitelist.
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If the source or destination database is a self-managed database (the Access Method is not Alibaba Cloud Instance), you must also click Test Connectivity in the CIDR Blocks of DTS Servers dialog box that appears.
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Configure the task objects.
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On the Configure Objects page, configure the objects that you want to migrate.
Configuration
Description
Migration Types
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If you only need to perform a full migration, select both Schema Migration and Full Data Migration.
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To perform a migration with no downtime, select Schema Migration, Full Data Migration, and Incremental Data Migration.
Note-
If you do not select Schema Migration, you must ensure that a database and tables to receive the data exist in the destination database. You can also use the object name mapping feature in the Selected Objects box as needed.
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If you do not select Incremental Data Migration, do not write new data to the source instance during data migration to ensure data consistency.
Method to Migrate Triggers in Source Database
Select a trigger migration method based on your needs. You can skip this step if your objects do not include triggers. For more information, see Configure trigger migration methods.
NoteThis option is available only when Migration Types includes both Schema Migration and Incremental Data Migration.
SQL Server Incremental Synchronization Mode
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Log-based Parsing for Non-heap Tables and CDC-based Incremental Synchronization for Heap Tables (Hybrid Log-based Parsing):
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Advantages:
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Supports scenarios that involve source heap tables, tables without primary keys, compressed tables, or tables with computed columns.
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Provides high link stability. This mode can obtain complete DDL statements and supports a wide range of DDL scenarios.
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Disadvantages:
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DTS creates the `dts_cdc_sync_ddl` trigger, the `dts_sync_progress` heartbeat table, and the `dts_cdc_ddl_history` DDL storage table in the source database. It also enables database-level CDC and CDC for some tables.
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You cannot execute `SELECT INTO`, `TRUNCATE`, or `RENAME COLUMN` statements on tables with CDC enabled in the source database. You cannot manually delete triggers created by DTS in the source database.
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Incremental Synchronization Based on Logs of Source Database (Heap tables are not supported):
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Advantage:
This mode is non-intrusive to the source database.
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Disadvantage:
This mode does not support scenarios that involve source heap tables, tables without primary keys, compressed tables, or tables with computed columns.
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Polling and querying CDC instances for incremental synchronization:
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Advantages:
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Supports full and incremental migration when the source database is Amazon RDS for SQL Server, Azure SQL Database, Azure SQL Managed Instance, Azure SQL Server on Virtual Machine, or Google Cloud SQL for SQL Server.
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This mode uses the native CDC component of SQL Server to obtain incremental data, which improves the stability of incremental migration and reduces network bandwidth usage.
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Disadvantages:
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The source database account used by the DTS instance must have the permissions to enable CDC. Incremental data migration has a latency of about 10 seconds.
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When you migrate multiple tables across multiple databases, you may encounter stability and performance issues.
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NoteThis option appears only when Migration Types includes Incremental Data Migration.
The maximum number of tables for which CDC is enabled that DTS supports.
Specify the maximum number of tables for which CDC can be enabled in this migration instance. The default value is 1,000.
NoteThis option does not appear when SQL Server Incremental Synchronization Mode is set to Incremental Synchronization Based on Logs of Source Database (Heap tables are not supported).
Processing Mode of Conflicting Tables
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Precheck and Report Errors: Checks whether tables with the same names exist in the destination database. If no tables with the same names exist, the precheck is passed. If tables with the same names exist, an error is reported during the precheck, and the data migration task does not start.
NoteIf a table in the destination database has the same name but cannot be easily deleted or renamed, you can change the name of the table in the destination database. For more information, see Object name mapping.
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Ignore Errors and Proceed: Skips the check for tables with the same names.
WarningSelecting Ignore Errors and Proceed may cause data inconsistency and business risks. For example:
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If the table schemas are consistent and a record in the destination database has the same primary key value as a record in the source database:
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During full migration, DTS keeps the record in the destination database. The record from the source database is not migrated.
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During incremental migration, DTS does not keep the record in the destination database. The record from the source database overwrites the record in the destination database.
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If the table schemas are inconsistent, only some columns of data may be migrated, or the migration may fail. Proceed with caution.
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Source Objects
In the Source Objects box, click the objects to migrate, and then click
to move them to the Selected Objects box.NoteThe granularity for selecting migration objects is schema, table, and column. If you select only tables or columns as migration objects, other objects such as views, triggers, and 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 Individual table column mapping.
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-
Using object name mapping may cause migration failures for dependent objects.
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To filter data using a WHERE condition, right-click the table that you want to migrate in the Selected Objects box and set the filter condition in the dialog box that appears. For more information, see Set filter conditions.
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To select SQL operations at the database or table level, right-click the object that you want to migrate in the Selected Objects box and select the required SQL operations in the dialog box that appears. The supported operations are listed in SQL operations supported for incremental migration.
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Click Next: Advanced Settings to configure advanced parameters.
Configuration
Description
Dedicated Cluster for Task Scheduling
By default, DTS schedules tasks on a shared cluster. You do not need to select one. If you want more stable tasks, you can purchase a dedicated cluster to run DTS migration tasks.
Retry Time for Failed Connections
After the migration task starts, if the connection to the source or destination database fails, DTS reports an error and immediately begins to retry the connection. The default retry duration is 720 minutes. You can customize the retry time to a value from 10 to 1440 minutes. We recommend that you set the duration to more than 30 minutes. If DTS reconnects to the source and destination databases within the specified duration, the migration task automatically resumes. Otherwise, the task fails.
Note-
For multiple DTS instances that share the same source or destination, the network retry time is determined by the setting of the last created task.
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Because you are charged for the task during the connection retry period, we recommend that you customize the retry time based on your business needs, or release the DTS instance as soon as possible after the source and destination database instances are released.
Retry Time for Other Issues
After the migration task starts, if a non-connectivity issue, such as a DDL or DML execution exception, occurs in the source or destination database, DTS reports an error and immediately begins to retry the operation. The default retry duration is 10 minutes. You can customize the retry time to a value from 1 to 1440 minutes. We recommend that you set the duration to more than 10 minutes. If the related operations succeed within the specified retry duration, the migration task automatically resumes. Otherwise, the task fails.
ImportantThe value of Retry Time for Other Issues must be less than the value of Retry Time for Failed Connections.
Enable Throttling for Full Data Migration
During full migration, DTS consumes read and write resources on the source and destination databases, which may increase the database load. If required, you can enable throttling for the full migration task. You can set Queries per second (QPS) to the source database, RPS of Full Data Migration, and Data migration speed for full migration (MB/s) to reduce the load on the destination database.
Note-
This configuration item is available only if you select Full Data Migration for Migration Types.
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You can also adjust the full migration speed after the migration instance is running.
Enable Throttling for Incremental Data Migration
If required, you can also choose to set speed limits for the incremental migration task. You can set RPS of Incremental Data Migration and Data migration speed for incremental migration (MB/s) to reduce the load on the destination database.
Note-
This configuration item is available only if you select Incremental Data Migration for Migration Types.
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You can also adjust the incremental migration speed after the migration instance is running.
Environment Tag
Select an environment label to identify the instance. This example does not require a label.
Configure ETL
Based on your business needs, select whether to configure the ETL feature to process data.
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Yes: Configures the ETL feature. You must also enter data processing statements in the text box.
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No: Does not configure the ETL feature.
Monitoring and Alerting
Select whether to set alerts and receive alert notifications based on your business needs.
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No: Does not set an alert.
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Yes: Configure alerts by setting an alert threshold and an alert notifications. If a migration fails or the latency exceeds the threshold, the system sends an alert notification.
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Click Next: Data Validation to configure a data validation task.
For more information about the data validation feature, see Configure data validation.
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Save the task and run a precheck.
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To view the parameters for configuring this instance when you call the API operation, move the pointer over the Next: Save Task Settings and Precheck button and click Preview OpenAPI parameters in the bubble that appears.
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If you do not need to view or have finished viewing the API parameters, click Next: Save Task Settings and Precheck at the bottom of the page.
Note-
Before the migration task starts, DTS performs a precheck. The task starts only after it passes the precheck.
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If the precheck fails, click View Details next to the failed check item, fix the issue based on the prompt, and then run the precheck again.
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If a warning is reported during the precheck:
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For check items that cannot be ignored, click View Details next to the failed item, fix the issue based on the prompt, and then run the precheck again.
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For check items that can be ignored, you can click Confirm Alert Details, Ignore, OK, and Precheck Again to skip the alert item and run the precheck again. If you choose to ignore a warning, it may cause issues such as data inconsistency and pose risks to your business.
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Purchase the instance.
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When the Success Rate is 100%, click Next: Purchase Instance.
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On the Purchase page, select the link specification for the data migration instance. For more information, see the following table.
Category
Parameter
Description
New Instance Class
Resource Group Settings
Select the resource group to which the instance belongs. The default value is default resource group. For more information, see What is Resource Management?
Instance Class
DTS provides migration specifications with different performance levels. The link specification affects the migration speed. You can select a specification based on your business scenario. For more information, see Data migration link specifications.
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After the configuration is complete, read and select Data Transmission Service (Pay-as-you-go) Service Terms.
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Click Buy and Start. In the OK dialog box that appears, click OK.
You can view the progress of the migration task on the Data Migration Tasks list page.
Note-
If the migration task does not include incremental migration, it stops automatically after the full migration is complete. After the task stops, its Status changes to Completed.
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If the migration task includes incremental migration, it does not stop automatically. The incremental migration task continues to run. While the incremental migration task is running, the Status of the task is Running.
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