Migrate incremental data from an Amazon RDS for PostgreSQL database to an ApsaraDB RDS for PostgreSQL database

Notes

• DTS uses read and write resources of the source and destination databases during full data migration. This may increase the loads of the database servers. If the database performance is unfavorable, the specification is low, or the data volume is large, database services may become unavailable. For example, DTS occupies a large amount of read and write resources in the following cases: a large number of slow SQL queries are performed on the source database, the tables have no primary keys, or a deadlock occurs in the destination database. Before you migrate data, evaluate the impact of data migration on the performance of the source and destination databases. We recommend that you migrate data during off-peak hours. For example, you can migrate data when the CPU utilization of the source and destination databases is less than 30%.
• The objects to be migrated must have PRIMARY KEY or UNIQUE constraints and all fields must be unique. Otherwise, duplicate data may exist in the destination database and migration may fail.
• A single data migration task can migrate data from only one database. To migrate data from multiple databases, you must create a data migration task for each database.
• Only data manipulation language (DML) operations, such as INSERT, UPDATE, DELETE, and UPDATE operations, can be migrated.
• During data migration, DTS creates a replication slot for the Amazon RDS for PostgreSQL database. The replication slot is prefixed with dts_sync_. DTS automatically clears historical replication slots every 90 minutes to prevent them from occupying disk space.
  Note If a migration task is released or fails, DTS automatically clears the replication slot. After a switchover between primary and secondary Amazon RDS for PostgreSQL databases, you must log on to the secondary database to manually clear the replication slot.
  
• DTS automatically resumes a failed data migration task. Before switching your workloads to the destination instance, you must stop or release the data migration task. Otherwise, the data from the source database will overwrite the data in the destination instance after the task is resumed.

Billing

Migration types

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

  Note Functions that are written in the C programming language cannot be migrated.
• Full data migration

  DTS migrates historical data of the required objects from the Amazon RDS for PostgreSQL database to the ApsaraDB RDS for PostgreSQL database.

• Incremental data migration

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

Permissions required for database accounts

Data migration process

To avoid data migration failures caused by dependencies between objects, DTS migrates the schemas and data of the source PostgreSQL database 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 performing incremental data migration, do not perform DDL operations on the objects to be migrated in the Amazon RDS for PostgreSQL database. Otherwise, the objects may fail to be migrated.

Preparations

1. Log on to the Amazon RDS Management Console.
2. In the upper-right corner of the page, select the region where 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 corresponding to the existing inbound rule.
   

Procedure

1. Log on to 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 information about the source and destination databases for the data migration task.
   

   Section	Parameter	Description
   N/A	Task Name	DTS automatically generates a task name. We recommend that you use an informative name for easy identification. You do not need to use a unique task name.
   Source Database	Instance Type	Select User-Created Database with Public IP Address.
   	Instance Region	Select the region where the source instance resides. If the instance type is set to User-Created Database with Public IP Address, you do not need to specify the instance region.
   	Database Type	Select PostgreSQL.
   	Hostname or IP Address	Enter the endpoint that is used to connect to the Amazon RDS for PostgreSQL database. Note You can find the endpoint on the Basic information page of the source Amazon RDS for PostgreSQL instance.
   	Port Number	Enter the service port number of the Amazon RDS for PostgreSQL database. The default port number is 5432.
   	Database Name	Enter the name of the source Amazon RDS for PostgreSQL database.
   	Database Account	Enter the account for the Amazon RDS for PostgreSQL database. For more information about permissions required for the account, see Permissions required for database accounts.
   	Database Password	Enter the password for the database account. Note After you specify the source database parameters, click Test Connectivity next to Database Password to verify whether the specified parameters are valid. If the specified parameters are valid, the Passed message appears. If the Failed message appears, click Check next to Failed. Modify the source database parameters based on the check results.
   Destination Database	Instance Type	Select RDS Instance.
   	Instance Region	Select the region where the destination ApsaraDB RDS for PostgreSQL instance resides.
   	RDS Instance ID	Select the ID of the destination ApsaraDB RDS for PostgreSQL instance.
   	Database Name	Enter the name of the destination ApsaraDB RDS for PostgreSQL database. The name can be different from the name of the source Amazon RDS for PostgreSQL database. Note Before you configure the data migration task, you must create a database in the ApsaraDB RDS for PostgreSQL instance. For more information, see Create a database.
   	Database Account	Enter the database account for the destination ApsaraDB RDS for PostgreSQL instance. For more information about permissions required for the account, see Permissions required for database accounts.
   	Database Password	Enter the password for the database account. Note After you specify the destination database parameters, click Test Connectivity next to Database Password to verify whether the specified parameters are valid. If the specified parameters are valid, the Passed message appears. If the Failed message appears, click Check next to Failed. Modify the destination database parameters based on the check results.

6. In the lower-right corner of the page, click Set Whitelist and Next.
   Note The CIDR blocks of DTS servers are automatically added to the whitelist of the destination ApsaraDB RDS for PostgreSQL instance. This ensures that DTS servers can connect to the destination ApsaraDB RDS for PostgreSQL instance.
7. Select the migration types and objects to be migrated.
   

   Parameter	Description
   Migration types	Select Schema Migration, Full Data Migration, and Incremental Data Migration.
   Objects to be migrated	Select objects from the Available section and click the icon to add the objects to the Selected section. Note You can select columns, tables, or schemas as the objects to be migrated. After an object is migrated to the destination database, the name of the object remains unchanged. You can change the name of an object in the destination ApsaraDB RDS for PostgreSQL instance by using the object name mapping feature provided by DTS. For more information about the authorization methods, see Object name mapping. If you use the object name mapping feature on an object, other objects that are dependent on the object may fail to be migrated.

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

   • Before you can start the data migration task, a precheck is performed. DTS can migrate data only if the precheck is past.
   • If the precheck fails, click the icon next to each failed item to view details. Fix the issues as prompted and run the precheck again.
9. After the precheck is past, 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 migration task.
    Note The migration task does not automatically end. You must manually stop the migration task. Select an appropriate time to manually stop the migration task. For example, you can stop the migration 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 appears in the progress bar of the migration task. Then, stop writing data to the source database for a few minutes. The delay time of incremental data migration may be displayed in the progress bar.
    2. After the status of incremental data migration changes to The migration task is not delayed, manually stop the migration task.
12. Switch your workloads to the ApsaraDB RDS for PostgreSQL instance.