Data Transmission Service:Migrate data from an Amazon RDS for Oracle instance to an ApsaraDB RDS for MySQL instance

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 instance will overwrite the data in the destination instance after the task is resumed.

Billing

Migration types

• Schema migration

  DTS supports schema migration for the following types of objects: table, index, constraint, and sequence. DTS does not support schema migration for the following types of objects: view, synonym, trigger, stored procedure, function, package, and user-defined type.

• Full data migration

  DTS migrates historical data of the required objects from the source database in the Amazon RDS for Oracle instance to the destination database in the ApsaraDB RDS for MySQL instance.

• Incremental data migration

  DTS retrieves redo log files from the source database in the Amazon RDS for Oracle instance. Then, DTS synchronizes incremental data from the source database in the Amazon RDS for Oracle instance to the destination database in the ApsaraDB RDS for MySQL instance. Incremental data migration allows you to ensure service continuity when you migrate data from an Oracle database.

SQL operations that can be synchronized during incremental data migration

• INSERT, DELETE, and UPDATE
• CREATE TABLE
  Note If a CREATE TABLE operation creates a partitioned table or a table that contains functions, DTS does not synchronize the operation.
• ALTER TABLE, including only 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 and authorize database account, see the following topics:

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

Data type mappings

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

Before you begin

1. Log on to the Amazon RDS Management Console.
2. Go to the Basic Information page of the 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 to add the CIDR blocks of DTS servers in the corresponding region to the inbound rule. For more information, see Add the CIDR blocks of DTS servers to the security settings of on-premises databases.
   

   Note

   • You need to add the CIDR blocks of DTS servers that only 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 need to add the CIDR blocks of DTS servers that only reside in the China (Hangzhou) region.
   • You can add all of the required CIDR blocks to the inbound rule at a time.
5. Modify the log settings of the Amazon RDS for Oracle instance. Skip this step if you do not need to perform incremental data migration.
   • If the database version of the Amazon RDS for Oracle instance is 12c or later (non-multitenant architecture), perform the following steps to configure the log settings:
     1. Use the master user account and the SQL*Plus tool to connect to the Amazon RDS for Oracle instance.
     2. Enable archive logging and supplemental logging.

        Type	Procedure
        Archive logging	Execute the following statement to check whether archive logging is enabled: SELECT LOG_MODE FROM v$database; Set a retention period for archived logs. Note We recommend that you set the retention period of archived logs to at least 72 hours. In this example, the retention period is set to 72 hours. exec rdsadmin.rdsadmin_util.show_configuration; exec rdsadmin.rdsadmin_util.set_configuration('archivelog retention hours', 72);
        Supplemental logging	Enable supplemental logging at the database or table level: Enable database-level supplemental logging Execute the following statement to check whether database-level supplemental logging is enabled: SELECT supplemental_log_data_min, supplemental_log_data_pk, supplemental_log_data_ui FROM v$database; Enable primary key and unique key supplemental logging at the database level: exec rdsadmin.rdsadmin_util.alter_supplemental_logging('ADD', 'PRIMARY KEY'); exec rdsadmin.rdsadmin_util.alter_supplemental_logging('ADD', 'UNIQUE'); Enable table-level supplemental logging by using one of the following methods: Enable table-level supplemental logging for all columns: exec rdsadmin.rdsadmin_util.alter_supplemental_logging('ADD', 'ALL'); Enable primary key supplemental logging at the table level: exec rdsadmin.rdsadmin_util.alter_supplemental_logging('ADD', 'PRIMARY KEY');

     3. Grant fine-grained permissions to the database account of the Amazon RDS for Oracle instance.
        Grant fine-grained permissions

        Webpack

        # Create a database account, for example, RDSDT_DTSACCT, and grant permissions to the account.
        create user RDSDT_DTSACCT IDENTIFIED BY RDSDT_DTSACCT;
        grant create session to RDSDT_DTSACCT;
        grant connect to RDSDT_DTSACCT;
        grant resource to RDSDT_DTSACCT;
        exec rdsadmin.rdsadmin_util.grant_sys_object('V_$LOGMNR_LOGS','RDSDT_DTSACCT','SELECT');
        exec rdsadmin.rdsadmin_util.grant_sys_object('ALL_OBJECTS','RDSDT_DTSACCT','SELECT');
        exec rdsadmin.rdsadmin_util.grant_sys_object('ALL_TAB_COLS','RDSDT_DTSACCT','SELECT');
        exec rdsadmin.rdsadmin_util.grant_sys_object('DBA_REGISTRY','RDSDT_DTSACCT','SELECT');
        grant select any table to RDSDT_DTSACCT;
        grant select any transaction to RDSDT_DTSACCT;
        -- v$log privileges
        exec rdsadmin.rdsadmin_util.grant_sys_object('V_$LOG','RDSDT_DTSACCT','SELECT');
        -- v$logfile privileges
        exec rdsadmin.rdsadmin_util.grant_sys_object('V_$LOGFILE','RDSDT_DTSACCT','SELECT');
        -- v$archived_log privileges
        exec rdsadmin.rdsadmin_util.grant_sys_object('V_$ARCHIVED_LOG','RDSDT_DTSACCT','SELECT');
        -- v$parameter privileges
        exec rdsadmin.rdsadmin_util.grant_sys_object('V_$PARAMETER','RDSDT_DTSACCT','SELECT');
        -- v$database privileges
        exec rdsadmin.rdsadmin_util.grant_sys_object('V_$DATABASE','RDSDT_DTSACCT','SELECT');
        -- v$active_instances privileges
        exec rdsadmin.rdsadmin_util.grant_sys_object('V_$ACTIVE_INSTANCES','RDSDT_DTSACCT','SELECT');
        -- v$instance privileges
        exec rdsadmin.rdsadmin_util.grant_sys_object('V_$INSTANCE','RDSDT_DTSACCT','SELECT');
        -- v$logmnr_contents privileges
        exec rdsadmin.rdsadmin_util.grant_sys_object('V_$LOGMNR_CONTENTS','RDSDT_DTSACCT','SELECT');
        exec rdsadmin.rdsadmin_util.grant_sys_object('USER$','RDSDT_DTSACCT','SELECT');
        exec rdsadmin.rdsadmin_util.grant_sys_object('OBJ$','RDSDT_DTSACCT','SELECT');
        exec rdsadmin.rdsadmin_util.grant_sys_object('COL$','RDSDT_DTSACCT','SELECT');
        exec rdsadmin.rdsadmin_util.grant_sys_object('IND$','RDSDT_DTSACCT','SELECT');
        exec rdsadmin.rdsadmin_util.grant_sys_object('ICOL$','RDSDT_DTSACCT','SELECT');
        exec rdsadmin.rdsadmin_util.grant_sys_object('CDEF$','RDSDT_DTSACCT','SELECT');
        exec rdsadmin.rdsadmin_util.grant_sys_object('CCOL$','RDSDT_DTSACCT','SELECT');
        exec rdsadmin.rdsadmin_util.grant_sys_object('TABPART$','RDSDT_DTSACCT','SELECT');
        exec rdsadmin.rdsadmin_util.grant_sys_object('TABSUBPART$','RDSDT_DTSACCT','SELECT');
        exec rdsadmin.rdsadmin_util.grant_sys_object('TABCOMPART$','RDSDT_DTSACCT','SELECT');
        grant LOGMINING TO RDSDT_DTSACCT;
        grant EXECUTE_CATALOG_ROLE to RDSDT_DTSACCT;
        exec rdsadmin.rdsadmin_util.grant_sys_object('DBMS_LOGMNR','RDSDT_DTSACCT','EXECUTE');
        grant select on v$database to rdsdt_dtsacct;
        grant select on dba_objects to rdsdt_dtsacct;
        grant select on DBA_TAB_COMMENTS to rdsdt_dtsacct;
        grant select on dba_tab_cols to rdsdt_dtsacct;
        grant select_catalog_role TO rdsdt_dtsacct;

   • If the database version of the Amazon RDS for Oracle instance is 9i, 10g, or 11g, perform the following steps to configure the log settings:
     1. Use the master user account and the SQL*Plus tool to connect to the Amazon RDS for Oracle instance.
     2. Run the archive log list; command to check whether the Amazon RDS for Oracle instance is running in ARCHIVELOG mode.
        Note If the instance is running in NOARCHIVELOG mode, switch the mode to ARCHIVELOG. 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;/

     7. Set a retention period for archived logs.
        Note We recommend that you set the retention period of archived logs to at least 24 hours.
     8. 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 automatically generates a task name. We recommend that you specify 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	If you select User-Created Database with Public IP Address as the instance type, you do not need to specify the Instance Region parameter.
   	Database Type	Select Oracle.
   	Hostname or IP Address	Enter the endpoint that is used to access the Amazon RDS for Oracle instance. Note You can obtain the endpoint on the Basic Information page of the Amazon RDS for Oracle instance.
   	Port Number	Enter the service port number of the Amazon RDS for Oracle instance. The default port number is 1521.
   	Instance Type	If you select Non-RAC Instance, you must specify the SID parameter. If you select RAC Instance, you must specify the Service Name parameter. In this example, select Non-RAC Instance and specify the SID.
   	Database Account	Enter the database account of the Amazon RDS for Oracle instance. For information about the permissions that are 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 is displayed. If the Failed message is displayed, 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 ApsaraDB RDS for MySQL instance resides.
   	RDS Instance ID	Select the ID of the ApsaraDB RDS for MySQL instance.
   	Database Account	Enter the database account of the ApsaraDB RDS for MySQL instance. For information about the permissions that are 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 is displayed. If the Failed message is displayed, 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.
   Warning

   • If the source or destination database instance is an Alibaba Cloud database instance, such as an ApsaraDB RDS for MySQL or ApsaraDB for MongoDB instance, or is a self-managed database hosted on Elastic Compute Service (ECS), DTS automatically adds the CIDR blocks of DTS servers to the whitelist of the database instance or ECS security group rules. For more information, see Add the CIDR blocks of DTS servers to the security settings of on-premises databases. If the source or destination database is a self-managed database on data centers or is from other cloud service providers, you must manually add the CIDR blocks of DTS servers to allow DTS to access the database.
   • If the CIDR blocks of DTS servers are automatically or manually added to the whitelist of the database instance or 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 account 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.
   • After the DTS task is completed or released, we recommend that you manually detect and remove the added CIDR blocks from the whitelist of the database instance or ECS security group rules.
7. Select the migration types and the objects to be migrated.
   

   Setting	Description
   Select the migration types	To perform only full data migration, select Schema Migration and Full Data Migration. To ensure service continuity during data migration, select Schema Migration, Full Data Migration, and Incremental Data Migration. Note If Incremental Data Migration is not selected, we recommend that you do not write data to the source database during data migration. This ensures data consistency between the source and destination databases.
   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 databases as the objects to be migrated. By default, after an object is migrated to the destination database, the name of the object remains unchanged. You can use the object name mapping feature to rename the objects that are migrated to the ApsaraDB RDS for MySQL instance. For more information, see Object name mapping. If you use the object name mapping feature to rename an object, other objects that are dependent 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 for failed connections 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 based on your needs. If DTS reconnects to the source and destination databases within the specified time, 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 based on your business needs. You can also release the DTS instance at your 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, a precheck is performed. 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.
    • Schema migration and full data migration

      We recommend that you do not manually stop the task during full data migration. Otherwise, the data migrated to the destination database will be incomplete. You can wait until the data migration task automatically stops.

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

      The task does not automatically stop during incremental data migration. You must manually stop the task.

      Important 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 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 of incremental data migration may be displayed in the progress bar.
      2. Wait until the status 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 MySQL instance.