PolarDB:Migrate self-managed Oracle to PolarDB for PostgreSQL (Compatible with Oracle)

Limitations

Billing

Migration types

Data type mapping

For more information, see Data type mapping between heterogeneous databases.

SQL operations for incremental migration

Prerequisites

Log on to the self-managed Oracle database to be migrated, create an account for data collection, and grant the necessary permissions to that account.

To create a database account and grant permissions:

• For a self-managed Oracle database, see Database account preparations, CREATE USER, and GRANT.

• For a PolarDB for PostgreSQL (Compatible with Oracle) cluster, see Create database accounts.

Procedure

1. Navigate to the migration task list page for the destination region using one of the following methods.

   From the DTS console

   1. Log on to the Data Transmission Service (DTS) console.

   2. In the navigation pane on the left, click Data Migration.

   3. In the upper-left corner of the page, select the region where the migration instance is located.

   From the DMS console

   Note

   The 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.

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

   2. In the top menu bar, choose Data + AI > Data Transmission (DTS) > Data Migration.

   3. To the right of Data Migration Tasks, select the region where the migration instance is located.

2. Click Create Task to navigate to the task configuration page.

3. 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.

   • The parameters on the new and old configuration pages are different. We recommend that you use the new configuration page.

4. Configure the source and destination databases.

   Warning

   After you select the source and destination instances, we recommend that you carefully read the limits displayed at the top of the page. Otherwise, the task may fail or data inconsistency may occur.

   Section	Parameter	Description
   N/A	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	Select the registered database instance with DTS from the drop-down list. The database information below is automatically configured. Note In the DMS console, this configuration item is Select a DMS database instance. If you have not registered the database instance or do not need to use a registered instance, manually configure the database information below.
   	Database Type	Select Oracle.
   	Access Method	Select the method based on where your source database is deployed. This example uses Self-managed Database on ECS. Note If your self-managed database is a different type, you must complete the corresponding preparations. For more information, see Overview of preparations.
   	Instance Region	Select the region where the source Oracle database is located.
   	ECS Instance ID	Select the ID of the ECS instance that hosts your source Oracle database.
   	Port Number	Enter the service port of the source Oracle database. The default value is 1521.
   	Oracle Type	Non-RAC Instance: If you select this option, you must also specify the SID. RAC or PDB Instance: If you select this option, you must also specify the Service Name. This example uses RAC or PDB Instance and a specified Service Name.
   	Database Account	Enter the database account for the self-managed Oracle database. For permission requirements, see Database account permissions.
   	Database Password	Enter the password for the database account.
   Destination Database	Select Existing Connection	Select the registered database instance with DTS from the drop-down list. The database information below is automatically configured. Note In the DMS console, this configuration item is Select a DMS database instance. If you have not registered the database instance or do not need to use a registered instance, manually configure the database information below.
   	Database Type	Select PolarDB (Compatible with Oracle).
   	Access Method	Select Alibaba Cloud Instance.
   	Instance Region	Select the region where the destination PolarDB for PostgreSQL (Compatible with Oracle) cluster is located.
   	Instance ID	Select the ID of the destination PolarDB for PostgreSQL (Compatible with Oracle) cluster.
   	Database Name	Enter the name of the database in the destination PolarDB for PostgreSQL (Compatible with Oracle) cluster where the migrated objects will be stored.
   	Database Account	Enter the database account for the destination PolarDB for PostgreSQL (Compatible with Oracle) cluster. For permission requirements, see Database account permissions.
   	Database Password	Enter the password for the database account.
   	Encryption	Select either Non-encrypted or SSL-encrypted based on your requirements. If you select SSL-encrypted, you must upload a CA Certificate.

5. After you complete the configuration, click Test Connectivity and Proceed at the bottom of the page. In the CIDR Blocks of DTS Servers dialog box that appears, click Test Connectivity.

   Note

   Ensure that the IP address segments of the DTS service are 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.

6. Configure the task objects.

   1. On the Configure Objects page, configure the objects that you want to migrate.

      Parameter	Description
      Migration Types	If you only need to perform a full migration, select both Schema Migration and Full Data Migration. 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. If you do not select Incremental Data Migration, do not write new data to the source instance during data migration to ensure data consistency.
      Add a hidden primary key for a table without a primary key/a table without a unique key	If a table to be migrated has neither a primary key nor a unique key, you must select Yes. DTS uses the ROWID from the Oracle database as a hidden primary key (a non-null unique key) in the destination table to prevent data duplication. Note This parameter can be configured only when Migration Types is selected for Schema Migration, along with at least one of Full Data Migration or Incremental Data Migration.
      Processing Mode for Existing Destination Tables	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. Note If 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. Ignore Errors and Proceed: Skips the check for tables with the same names. Warning Selecting Ignore Errors and Proceed may cause data inconsistency and business risks. For example: 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: During full migration, DTS keeps the record in the destination database. The record from the source database is not migrated. 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. If the table schemas are inconsistent, only some columns of data may be migrated, or the migration may fail. Proceed with caution.
      Source Objects	In the Source Objects box, click the objects to migrate, and then click to move them to the Selected Objects box.
      Selected Objects	To change the name of a single migration object in the target instance, right-click the object in the Selected Objects box. For more information, see Map individual schema, table, and column names. To change the names of multiple migration objects in the target instance, click Selected Objects in the upper-right corner of the Batch Edit box. For more information, see Map multiple schema, table, and column names. Note If you use the object name mapping feature, other objects that depend on the renamed object may fail to migrate. To filter data by using WHERE clauses, right-click a table in the Selected Objects panel and specify the filter conditions in the dialog box that appears. For more information, see Set filter conditions. To select the SQL operations for incremental data migration at the database or table level, right-click the desired object in the Selected Objects panel and select the SQL operations in the dialog box that appears.

   2. Click Next: Advanced Settings to configure advanced parameters.

      Parameter	Description
      Dedicated Cluster for Task Scheduling	By default, DTS schedules the task on a shared cluster, so you do not need to select one. You can purchase a dedicated cluster with specific specifications to run DTS migration tasks. For more information, see What is a DTS dedicated cluster?
      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. 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. Important The 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. 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. You can also adjust the incremental migration speed after the migration instance is running.
      Environment Tag	You can select an environment tag to identify the instance based on your business requirements. No tag is selected in this example.
      Actual Write Code	You can select the character encoding for writing data to the destination based on your business requirements.
      Configure ETL	Choose whether to enable the extract, transform, and load (ETL) feature. For more information, see What is ETL? Valid values: Yes: Enables the ETL feature. Enter data processing statements in the code editor. For more information, see Configure ETL in a data migration or data synchronization task. No: Disables the ETL feature.
      Monitoring and Alerting	Select whether to set alerts and receive alert notifications based on your business needs. No: Does not set an alert. 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.

   3. Click Next: Data Validation to configure a data validation task.

      For more information about the data validation feature, see Configure data validation.

7. After you complete the configurations, click Next: Save Task Settings and Precheck at the bottom of the page.

   You can move the pointer over the Next: Save Task Settings and Precheck button and click Preview OpenAPI parameters in the bubble that appears to view the parameters for configuring this instance when you call the API operation.

   Note

   • Before the migration task starts, DTS performs a precheck. The task starts only after it passes the precheck.

   • 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.

   • If a warning is reported during the precheck:

     • 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.

     • 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.

8. Purchase the instance.

   1. When the Success Rate is 100%, click Next: Purchase Instance.

   2. 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.

   3. After the configuration is complete, read and select Data Transmission Service (Pay-as-you-go) Service Terms.

   4. 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.

      • 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.

Next steps

If you set the Add a hidden primary key for a table without a primary key/a table without a unique key option to Yes, you must manually delete the hidden primary key that DTS adds. After switching your workloads to the destination database and before stopping or releasing the DTS instance, go to the Basic Information tab of the Full Data Migration or Incremental Write module and click Delete Invisible Primary Key in the Actions column.