Migrate data from an Amazon RDS for Oracle database to an ApsaraDB RDS for MySQL database

Precautions

• 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.
• DTS uses the ROUND(COLUMN,PRECISION) function to retrieve values from columns of the FLOAT or DOUBLE data type. If you do not specify a precision, DTS sets the precision for the FLOAT data type to 38 digits and the precision for the DOUBLE data type to 308 digits. You must check whether the precision settings meet your business requirements.
• DTS automatically creates a destination database in the ApsaraDB RDS for MySQL instance. However, if the name of the source database is invalid, you must manually create a database in the ApsaraDB RDS for MySQL instance before you configure the data migration task.
  Note For more information about the naming conventions of ApsaraDB RDS for MySQL databases and how to create a database, see Create a database on an ApsaraDB RDS for MySQL instance.
• 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 database will overwrite the data in the destination instance after the task is resumed.

Billing

Migration types

• Schema migration

  DTS supports schema migration of tables, indexes, constraints, and sequences. However, DTS does not support schema migration of views, synonyms, triggers, stored procedures, stored functions, packages, and custom object types.

• Full data migration

  DTS migrates full data of objects to be migrated from the Amazon RDS for Oracle database to the database in the ApsaraDB RDS for MySQL instance.

• Incremental data migration

  During full data migration, DTS polls and captures the redo log files from the Amazon RDS for Oracle database. After the full data migration is complete, DTS synchronizes incremental data from the Amazon RDS for Oracle database to the destination ApsaraDB RDS for MySQL database. Incremental data migration helps you achieve service continuity when migrating data from an Amazon RDS for Oracle database to the destination database.

SQL operations that can be synchronized during incremental data migration

• INSERT, DELETE, and UPDATE
• CREATE TABLE
  Note The operations on tables or partitions that contain computed columns cannot be synchronized.
• ALTER TABLE operations, including ADD COLUMN, DROP COLUMN, RENAME COLUMN, and ADD INDEX
• DROP TABLE
• RENAME TABLE, TRUNCATE TABLE, and CREATE INDEX

Permissions required for database accounts

For more information about how to create a database account and grant permissions to the account, see the following topics:

• CREATE USER and GRANT for an Amazon RDS for Oracle database
• Create accounts and databases for an RDS for MySQL instance

Data type mappings

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

Preparation

1. Log on to the Amazon RDS Management Console.
2. Go to the Basic Information page of the source Amazon RDS for Oracle instance.
3. In the Security group rules section, click the name of the security group corresponding to the existing inbound rule.
   
4. On the Security Groups page, click the Inbound tab in the Security Group section. On the Inbound tab, click Edit, and add CIDR blocks of DTS servers to the Edit inbound rules dialog box that appears. The CIDR blocks of DTS servers vary with the region where the destination database resides. For more information about the CIDR blocks of DTS servers, see Add the CIDR blocks of DTS servers to the security settings of on-premises databases.
   

   Note

   • You only need to add 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 (Singapore) region and the destination database resides in the China (Hangzhou) region. You only need to add 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.
5. Change log configurations for the Amazon RDS for Oracle database. Skip this step if you do not need to perform incremental data migration.
   1. Use the master user account and the SQL*Plus tool provided by Oracle to connect to the Amazon RDS for Oracle database.
   2. Run the archive log list; command to check whether archiving is enabled for the Amazon RDS for Oracle database.
      Note If archiving is disabled for the instance, enable the archiving mode. For more information, see Managing Archived Redo Logs.
   3. Enable force logging.

      exec rdsadmin.rdsadmin_util.force_logging(p_enable => true);

   4. Enable supplemental logging for primary keys.

      begin rdsadmin.rdsadmin_util.alter_supplemental_logging(p_action => 'ADD',p_type => 'PRIMARY KEY');end;/

   5. Enable supplemental logging for unique keys.

      begin rdsadmin.rdsadmin_util.alter_supplemental_logging(p_action => 'ADD',p_type => 'UNIQUE');end;/

   6. Set a retention period for archived logs.

      begin rdsadmin.rdsadmin_util.set_configuration(name => 'archivelog retention hours', value => '24');end;/

      Note We recommend that you set the retention period of archived logs to at least 24 hours.
   7. Commit the changes.

      commit;

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 source and destination databases.
   

   Section	Parameter	Description
   N/A	Task Name	DTS generates a random task name. However, we recommend that you specify an informative name to ease management.
   Source Database	Instance Type	Select User-Created Database with Public IP Address.
   	Instance Region	When the instance type is set to User-Created Database with Public IP Address, you do not need to set Instance Region.
   	Database Type	Select Oracle.
   	Hostname or IP Address	Enter the endpoint for accessing the Amazon RDS for Oracle database. Note You can obtain the endpoint on the Basic information page of the source Amazon RDS for Oracle database.
   	Port Number	Enter the port number configured for the Amazon RDS for Oracle database. The default port number is 1521.
   	Instance Type	Non-RAC Instance: If you select this option, you must specify the SID. RAC Instance: If you select this option, you must specify the Service Name. In this example, select Non-RAC Instance and enter SID.
   	Database Account	Enter the account for the Amazon RDS for Oracle database. For more information about permissions required for the account, see Permissions required for database accounts.
   	Database Password	Enter the password of 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 MySQL instance resides.
   	RDS Instance ID	Select the RDS instance ID.
   	Database Account	Enter the database account of the ApsaraDB RDS for MySQL instance. For more information about permissions required for the account, see Permissions required for database accounts.
   	Database Password	Enter the password of 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 DTS adds the CIDR blocks of DTS servers to the whitelist of the ApsaraDB RDS for MySQL instance. This ensures that DTS servers can connect to the ApsaraDB RDS for MySQL instance.
7. Configure migration types and objects.
   

   Section	Description
   Migration Types	To perform only full data migration, select Schema Migration and Full Data Migration. To achieve service continuity during migration, select Schema Migration, Full Data Migration, and Incremental Data Migration. Note If Incremental Data Migration is not selected, do not write data into the source database during full data migration. This ensures data consistency between the source and destination databases.
   Objects to be migrated	Select the objects to be migrated in the Available section and click to move them to the Selected section. Note Objects to be migrated can be databases, tables, or columns. By default, the selected objects are not renamed after the migration. If you want to rename the objects that are migrated to the destination instance, you can use the object name mapping feature provided by DTS. For more information about how to use this feature, see Object name mapping. If you use the object name mapping feature for an object, objects that depend 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 data migration task.
    • Schema migration and full data migration

      Do not manually stop the migration task. Otherwise, the data may be incomplete. You need only to wait until the migration task is complete. The migration task can automatically stop.

    • Schema migration, full data migration, and incremental data migration

      The migration task cannot automatically stop. You must manually stop the migration task.

      Notice Manually stop the migration task at an appropriate time. For example, you can stop the migration task during off-peak hours of your business or before you switch your business to the destination cluster.
      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 delay time may appear in the status for incremental migration.
      2. Wait until the status of Incremental Data Migration for the migration task changes to The migration task is not delayed again. Then, manually stop the migration task.
12. Switch your workloads to the ApsaraDB RDS for MySQL database.