Data Transmission Service:Migrate incremental data from an Amazon RDS for PostgreSQL instance to an ApsaraDB RDS for PostgreSQL instance

Limits

• 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 objects 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 and data migration may fail.

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

• In this scenario, DTS can migrate only DML operations, such as the INSERT, DELETE, and UPDATE operations.

• During data migration, DTS creates a replication slot for the Amazon RDS for PostgreSQL instance. The replication slot is prefixed with dts_sync_. DTS automatically clears historical data in the replication slot every 90 minutes to reduce storage usage.

  Note

  If the data migration task is released or fails, DTS automatically clears the replication slot. If a primary/secondary switchover is performed on the Amazon RDS for PostgreSQL instance, you must log on to the secondary database to clear the replication slot.

  

• If a primary/secondary switchover is performed on the Amazon RDS for PostgreSQL instance, the DTS task fails and may fail to be resumed.

• If a data migration task fails, 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 instance overwrites the data in the destination instance after the task is resumed.

Billing rules

Migration types

• Schema migration

  DTS migrates the schemas of objects to the ApsaraDB RDS for PostgreSQL instance. DTS supports schema migration for the following types of objects: table, trigger, view, sequence, function, user-defined type, rule, domain, operation, and aggregate.

  Note

  DTS does not migrate functions that are written in the C programming language.

• Full data migration

  DTS migrates the existing data of objects from the Amazon RDS for PostgreSQL instance to the ApsaraDB RDS for PostgreSQL instance.

• Incremental data migration

  After full data migration is complete, DTS migrates incremental data from the Amazon RDS for PostgreSQL instance to the ApsaraDB RDS for PostgreSQL instance. Incremental data migration allows you to ensure service continuity when you migrate data from the Amazon RDS for PostgreSQL instance to the ApsaraDB RDS for PostgreSQL instance.

Permissions required for database accounts

Data migration process

To prevent data migration failures caused by dependencies between objects, DTS migrates the schemas and data of the source Amazon RDS for PostgreSQL instance in the following order:

1. Migrate the schemas of tables, views, sequences, functions, user-defined types, rules, domains, operations, and aggregates.

2. Perform full data migration.

3. Migrate the schemas of triggers and foreign keys.

4. Perform incremental data migration.

   Note

   Before incremental data migration, do not perform DDL operations on the objects in the Amazon RDS for PostgreSQL instance. Otherwise, the objects may fail to be migrated.

Before you begin

1. Log on to the Amazon RDS Management Console.

2. In the upper-right corner of the page, select the region in which the destination instance resides.

3. In the left-side navigation pane, click Databases. On the page that appears, click the ID of the destination database. The basic information page appears.

   

4. In the Security group rules section, click the name of the security group to which the existing inbound rule belongs.

   

5. On the Security Groups page, click the Inbound tab in the Security Group section. On the Inbound tab, click Edit. In the Edit inbound rules dialog box, add the CIDR blocks of DTS servers that reside in the corresponding region to the inbound rule. For more information, see Add the CIDR blocks of DTS servers.

   

   Note

   • You need to add only the CIDR blocks of DTS servers that reside in the same region as the destination database. For example, the source database resides in the Singapore region and the destination database resides in the China (Hangzhou) region. You need to add only the CIDR blocks of DTS servers that reside in the China (Hangzhou) region.

   • You can add all of the required CIDR blocks to the inbound rule at a time.

   • If you have other questions, see the official documentation of Amazon or contact technical support.

Procedure (in the new DTS console)

1. Go to the Data Migration page.

   1. Log on to the Data Management (DMS) console.

   2. In the top navigation bar, move the pointer over DTS.

   3. Choose DTS (DTS) > Data Migration.

   Note

   • The actual operations may vary based on the mode and layout of the DMS console. For more information, see Simple mode and Customize the layout and style of the DMS console.

   • You can also go to the Data Migration page of the new DTS console.

2. From the drop-down list on the right side of Data Migration Tasks, select the region in which your data migration instance resides.

   Note

   If you use the new DTS console, you must select the region in which the data migration instance resides in the upper-left corner.

3. Click Create Task. On the Create Task wizard page, configure the source and destination databases.

   Warning

   After you configure the source and destination databases, we recommend that you read the Limits that are displayed in the upper part of the page. Otherwise, the task may fail or data inconsistency may occur.

   Section	Parameter	Description
   N/A	Task Name	The name of the task. DTS automatically generates a task name. We recommend that you specify an informative name to identify the task. You do not need to specify a unique task name.
   Source Database	Select an existing DMS database instance	The database instance that you want to use. You can choose whether to use an existing instance based on your business requirements. If you select an existing instance, DTS automatically populates the parameters for the database. If you do not select an existing instance, you must manually configure parameters for the database.
   	Database Type	The type of the source database. Select PostgreSQL.
   	Access Method	The access method of the source database. Select Public IP Address.
   	Instance Region	The region in which the Amazon RDS for PostgreSQL instance resides. Note If the region in which the Amazon RDS for PostgreSQL instance resides is not displayed in the drop-down list, select a region that is geographically closest to the Amazon RDS for PostgreSQL instance.
   	Hostname or IP Address	The endpoint that is used to access the Amazon RDS for PostgreSQL instance. Note You can obtain the endpoint on the basic information page of the Amazon RDS for PostgreSQL instance.
   	Port Number	The service port number of the Amazon RDS for PostgreSQL instance. Default value: 5432.
   	Database Name	The name of the source database in the Amazon RDS for PostgreSQL instance.
   	Database Account	The database account of the Amazon RDS for PostgreSQL instance. For information about the permissions that are required for the account, see the Permissions required for database accounts section of this topic.
   	Database Password	The password that is used to access the database instance.
   Destination Database	Select an existing DMS database instance	The database instance that you want to use. You can choose whether to use an existing instance based on your business requirements. If you select an existing instance, DTS automatically populates the parameters for the database. If you do not select an existing instance, you must manually configure parameters for the database.
   	Database Type	The type of the destination database. Select PostgreSQL.
   	Access Method	The access method of the destination database. Select Alibaba Cloud Instance.
   	Instance Region	The region in which the destination ApsaraDB RDS for PostgreSQL instance resides.
   	Instance ID	The ID of the destination ApsaraDB RDS for PostgreSQL instance.
   	Database Name	The name of the destination database in the ApsaraDB RDS for PostgreSQL instance. The name can be different from the name of the source database in the Amazon RDS for PostgreSQL instance. Note Before you configure the data migration task, make sure that the destination database is created in the ApsaraDB RDS for PostgreSQL instance. For more information, see Create a database.
   	Database Account	The database account of the destination ApsaraDB RDS for PostgreSQL instance. For information about the permissions that are required for the account, see the Permissions required for database accounts section of this topic.
   	Database Password	The password that is used to access the database instance.

4. In the lower part of the page, click Test Connectivity and Proceed.

5. If an IP address whitelist is configured for your self-managed database, add the CIDR blocks of DTS servers to the IP address whitelist. Then, click Test Connectivity.

   Warning

   If the public CIDR blocks of DTS servers are automatically or manually added to the whitelist of a database instance or to the security group rules of an ECS instance, 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 security group rules and forbidding unauthorized CIDR blocks, or connecting the database instance to DTS by using Express Connect, VPN Gateway, or Smart Access Gateway.

6. Configure the objects to be migrated and the advanced settings.

   Parameter	Description
   Migration Types	Select Schema Migration and Incremental Migration. We recommend that you select all of the supported migration types.
   Processing Mode of Conflicting Tables	Precheck and Report Errors: checks whether the destination database contains tables that use the same names as tables in the source database. If the source and destination databases do not contain tables that have identical table names, the precheck is passed. Otherwise, an error is returned during the precheck and the data migration task cannot be started. Note If the source and destination databases contain tables with identical names and the tables in the destination database cannot be deleted or renamed, you can use the object name mapping feature to rename the tables that are migrated to the destination database. 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 the following potential risks: If the source and destination databases have the same schema, and a data record has the same primary key as an existing data record in the destination database, the following scenarios may occur: During full data migration, DTS does not migrate the data record to the destination database. The existing data record in the destination database is retained. During incremental data migration, DTS migrates the data record to the destination database. The existing data record in the destination database is overwritten. If the source and destination databases have different schemas, only specific columns are migrated or the data migration task fails. Proceed with caution.
   Capitalization of Object Names in Destination Instance	The capitalization of database names, table names, and column names in the destination instance. By default, DTS default policy is selected. You can select other options to make sure that the capitalization of object names is consistent with that of the source or destination database. For more information, see Specify the capitalization of object names in the destination instance.
   Source Objects	Select one or more objects from the Source Objects section. Click the icon and 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 depend on the object may fail to be migrated. To specify WHERE conditions to filter data, right-click a table in the Selected Objects section. In the dialog box that appears, specify the conditions. For more information, see Specify filter conditions. To migrate the SQL operations performed on a specific database or table, right-click the object in the Selected Objects section. In the dialog box that appears, select the SQL operations that you want to migrate.

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

   • Data Verification Settings

     For more information about how to use the data verification feature, see Configure a data verification task.

   • Advanced Settings

     Parameter	Description
     Dedicated Cluster for Task Scheduling	By default, DTS schedules the task to a shared cluster. You do not need to configure this parameter. You can purchase a dedicated cluster of the specified specifications to run data migration tasks. For more information, see What is a DTS dedicated cluster?
     Monitoring and Alerting	Specifies whether to configure alerting for the data migration task. If the task fails or the migration latency exceeds the specified threshold, the alert contacts receive notifications. Valid values: No: does not configure alerting. Yes: configures alerting. In this case, you must also configure the alert threshold and alert notification settings. For more information, see Configure monitoring and alerting when you create a DTS task.
     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 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.
     Retry Time for Other Issues	The retry time range for other issues. For example, if DDL or DML operations fail to be performed after the data migration task is started, DTS immediately retries the operations within the retry time range. Valid values: 1 to 1440. Unit: minutes. Default value: 10. We recommend that you set the parameter to a value greater than 10. If the failed operations are successfully performed within the specified retry time range, DTS resumes the data migration task. Otherwise, the change tracking task fails. Important The value of the Retry Time for Other Issues parameter must be smaller than the value of the Retry Time for Failed Connections parameter.
     Enable Throttling for Full Data Migration	During full data migration, DTS uses the read and write resources of the source and destination databases. This may increase the loads on the database servers. You can specify whether to enable throttling for the full data migration task. If you select Yes, you can configure the Queries per second (QPS) to the source database, RPS of Full Data Migration, and BPS of Full Data Migration parameters based on your business requirements to relieve the load on the destination instance. Note You can configure this parameter only when you select Full Data Migration as a migration type.
     Enable Throttling for Incremental Data Migration	You can specify whether to enable throttling for the incremental data migration task. If you select Yes, you can configure the RPS of Incremental Data Migration and BPS of Incremental Data Migration parameters based on your business requirements to relieve the load on the destination instance. Note You can configure this parameter only when you select Incremental Data Migration as a migration type.
     Configure ETL	Specifies whether to enable 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.

8. In the lower part of the page, click Next: Save Task Settings and Precheck.

   You can move the pointer over Next: Save Task Settings and Precheck and click Preview OpenAPI parameters to view the parameters to be specified when you call the relevant API operation to configure the DTS task.

   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 results, troubleshoot the issues. Then, run a precheck again.

   • If an alert is triggered for an item during the precheck:

     • If an alert item cannot be ignored, click View Details next to the failed item and troubleshoot the issues. Then, run a precheck again.

     • If the alert item can be ignored, click Confirm Alert Details. In the View Details dialog box, 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.

9. Wait until Success Rate becomes 100%. Then, click Next: Purchase Instance.

10. On the Purchase Instance page, configure the Instance Class parameter for the data migration instance. The following table describes the parameters.

    Section	Parameter	Description
    New Instance Class	Resource Group Settings	The resource group to which the data migration instance belongs. Default value: default resource group. For more information, see What is Resource Management?
    	Instance Class	DTS provides instance classes that vary in the migration speed. You can select an instance class based on your business scenario. For more information, see Specifications of data migration instances.

11. Read and agree to Data Transmission Service (Pay-as-you-go) Service Terms by selecting the check box.

12. Click Buy and Start. In the dialog box that appears, click OK.

    You can view the progress of the task in the task list.

Procedure (in the old DTS console)

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. At the top of the Migration Tasks page, select the region where the destination cluster 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 instance type of the source database. Select User-Created Database with Public IP Address.
   	Instance Region	The region in which the source instance resides. If you select User-Created Database with Public IP Address as the instance type, you do not need to configure the Instance Region parameter.
   	Database Type	The type of the source database. Select PostgreSQL.
   	Hostname or IP Address	The endpoint that is used to access the Amazon RDS for PostgreSQL instance. Note You can obtain the endpoint on the basic information page of the Amazon RDS for PostgreSQL instance.
   	Port Number	The service port number of the Amazon RDS for PostgreSQL instance. Default value: 5432.
   	Database Name	The name of the source database in the Amazon RDS for PostgreSQL instance.
   	Database Account	The database account of the Amazon RDS for PostgreSQL instance. For information about the permissions that are required for the account, see the Permissions required for database accounts of this topic.
   	Database Password	The password of the database account. Note After you configure the source database parameters, click Test Connectivity next to Database Password to verify whether the configured parameters are valid. If the configured parameters are valid, the Passed message is displayed. If the Failed message is displayed, click Check next to Failed to modify the source database parameters based on the check results.
   Destination Database	Instance Type	The instance type of the destination database. Select RDS Instance.
   	Instance Region	The region in which the ApsaraDB RDS for PostgreSQL instance resides.
   	RDS Instance ID	The ID of the ApsaraDB RDS for PostgreSQL instance.
   	Database Name	The name of the destination database in the ApsaraDB RDS for PostgreSQL instance. The name can be different from the name of the source database in the Amazon RDS for PostgreSQL instance. Note Before you configure the data migration task, make sure that the destination database is created in the ApsaraDB RDS for PostgreSQL instance. For more information, see Create a database.
   	Database Account	The database account of the ApsaraDB RDS for PostgreSQL instance. For information about the permissions that are required for the account, see the Permissions required for database accounts section of this topic.
   	Database Password	The password of the database account. Note After you configure the destination database parameters, click Test Connectivity next to Database Password to verify whether the configured parameters are valid. If the configured parameters are valid, the Passed message is displayed. If the Failed message is displayed, click Check next to Failed to modify the destination database parameters based on the check results.

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

   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 IP address 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, and you must make sure that the ECS instance can access the database. If the self-managed database is hosted on multiple ECS instances, you must manually add the CIDR blocks of DTS servers to the security group rules of each ECS instance. 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 IP address whitelist of the database to allow DTS to access the database. For more information, see the CIDR blocks of DTS servers section of the Add the CIDR blocks of DTS servers topic.

   Warning

   If the public CIDR blocks of DTS servers are automatically or manually added to the whitelist of a database instance or to the security group rules of an ECS instance, 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 security group rules and forbidding unauthorized CIDR blocks, or connecting the database instance to DTS by using Express Connect, VPN Gateway, or Smart Access Gateway.

   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	Select Schema Migration, Full Data Migration, and Incremental Data Migration.
   Select the objects to be migrated	Select one or more objects from the Available section and click the icon to move the objects to the Selected section. Note You can select columns, tables, or schemas as the objects to be migrated. By default, after an object is migrated to the destination database, the name of the object remains unchanged in the destination database. You can use the object name mapping feature to rename the objects that are migrated to the ApsaraDB RDS for PostgreSQL instance. For more information, see Object name mapping. If you use the object name mapping feature to rename an object, other objects that depend 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 a failed connection to the source or destination database	By default, if DTS fails to connect to the source or destination database, DTS retries within the next 12 hours. You can specify the retry time range based on your business requirements. 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 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 the earliest opportunity after the source and destination instances are released.

8. In the lower-right corner of the page, click 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.

9. After the task passes the precheck, click Next.

10. In the Confirm Settings dialog box, specify the Channel Specification parameter and select Data Transmission Service (Pay-As-You-Go) Service Terms.

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

    Note

    An incremental data migration task does not automatically stop. You must manually stop the task. We recommend that you select an appropriate time to manually stop the data migration task. For example, you can stop the task during off-peak hours or before you switch your workloads to the destination instance.

    1. Wait until Incremental Data Migration and The migration task is not delayed appear in the progress bar of the 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 state of incremental data migration changes to The migration task is not delayed again. Then, manually stop the migration task.

12. Switch your workloads to the ApsaraDB RDS for PostgreSQL instance.