Migrate data from a self-managed Oracle database to a PolarDB for MySQL cluster

Prerequisites

• The version of the self-managed Oracle database is 9i, 10g, 11g, 12c, 18c, or 19c.
• Supplemental logging, including SUPPLEMENTAL_LOG_DATA_PK and SUPPLEMENTAL_LOG_DATA_UI, is enabled for the self-managed Oracle database. For more information, see Supplemental Logging.
• The self-managed Oracle database is running in ARCHIVELOG mode. Archived log files are accessible and a suitable retention period is set for archived log files. For more information, see Managing Archived Redo Log Files.
• The available storage space of the PolarDB for MySQL cluster is larger than the total size of the data in the self-managed Oracle 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.
• If a data migration task fails, DTS automatically resumes the task. Before you switch your workloads to the destination cluster, stop or release the data migration task. Otherwise, the data in the source database will overwrite the data in the destination cluster after the task is resumed.
• Table names in the PolarDB for MySQL cluster are case-insensitive. If a table name in the source Oracle database contains uppercase letters, PolarDB for MySQL converts all uppercase letters to lowercase letters before creating the table.

  If the source Oracle database contains identical table names that differ only in capitalization, these table names are identified as duplicate. During schema migration, the following message is returned: "The object already exists." To prevent name conflicts in the destination database, you can change the names of the migrated objects by using the object name mapping feature. For more information, see Object name mapping.

• DTS automatically creates a destination database in the PolarDB for MySQL cluster. However, if the name of the source database is invalid, you must manually create a database in the PolarDB for MySQL cluster before you configure the data migration task. For more information about how to create a database and the database naming conventions, see Create a database.

Billing

Migration types

• Schema migration
  DTS supports schema migration for tables and indexes. DTS does not support schema migration for the following types of objects: view, synonym, trigger, stored procedure, function, package, and user-defined type. DTS has the following limits on schema migration for tables and indexes:

  • Schema migration of nested tables is not supported. Clustered tables and index-organized tables (IOTs) are converted into common tables in the destination database.
  • Schema migration of function-based indexes, domain indexes, bitmap indexes, and reverse indexes is not supported.
• Full data migration

  DTS migrates historical data of the required objects from the self-managed Oracle database to the destination database in the PolarDB for MySQL cluster.

• Incremental data migration

  DTS retrieves redo log files from the self-managed Oracle database. Then, DTS synchronizes incremental data from the self-managed Oracle database to the destination database in the PolarDB for MySQL cluster. Incremental data migration allows you to ensure service continuity when you migrate data from an Oracle database.

Data type conversion

Oracle and PolarDB for MySQL are heterogeneous databases. DTS does not ensure that the schemas of the source and destination databases are consistent after schema migration. We recommend that you evaluate the impact of data type conversion on your business. For more information, see Data type mappings between heterogeneous databases.

Before you begin

Log on to the source Oracle database, create an account for data collection, and grant permissions to the account.

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

• Self-managed Oracle database: CREATE USER and GRANT
• PolarDB for MySQL cluster: Create a database account and Manage database accounts for a cluster

create session;
connect;
resource;
execute on sys.dbms_logmnr;
select on v_$logmnr_contents;
select on v_$log;
select on v_$logfile;
select on v_$archived_log;
select on v_$logmnr_logs;
select on v_$parameter;
select on v_$database;
select on all_objects;
select on all_tab_cols;
select on dba_registry;
select any table;
select any transaction;
select on v$active_instances;
select on v$instance;
select on sys.USER$;
select on SYS.OBJ$;
select on SYS.COL$;
select on SYS.IND$;
select on SYS.ICOL$;
select on SYS.CDEF$;
select on SYS.CCOL$;
select on SYS.TABPART$;
select on SYS.TABSUBPART$;
select on SYS.TABCOMPART$;
select on gv_$listener_network;

# Grant permissions on the pluggable database (PDB) and container database (CDB).
# Grant permissions on the PDB:
create   session;
connect;
resource;
select on  all_objects;
select on  all_tab_cols;
select on  dba_registry;
select any table;
select any transaction;
select on v_$log;
select on v_$logfile;
select on v_$archived_log;
select on v_$parameter;
select on v_$database;
select on v_$active_instances;
select on v_$instance;
select on V_$PDBS;
select on sys.USER$;
select on SYS.OBJ$;
select on SYS.COL$;
select on SYS.IND$;
select on SYS.ICOL$;
select on SYS.CDEF$;
select on SYS.CCOL$;
select on SYS.TABPART$;
select on SYS.TABSUBPART$;
select on SYS.TABCOMPART$;

# Grant permissions on the CDB:
create   session;
LOGMINING;
select on v_$logmnr_contents;

# The following sample statements show you how to grant permissions to a database account named dtstest.
create user dtstest IDENTIFIED BY rdsdt_dtsacct;
grant create session to dtstest;
grant connect to dtstest;
grant resource to dtstest;
grant execute on sys.dbms_logmnr to dtstest;
grant select on v_$logmnr_contents to dtstest;
grant select on v_$log to dtstest;
grant select on v_$logfile to dtstest;
grant select on v_$archived_log to dtstest;
grant select on v_$logmnr_logs to dtstest;
grant select on v_$parameter to dtstest;
grant select on v_$database to dtstest;
grant select on all_objects to dtstest;
grant select on all_tab_cols to dtstest;
grant select on dba_registry to dtstest;
grant select any table to dtstest;
grant select any transaction to dtstest;
grant select on v$active_instances to dtstest;
grant select on v$instance to dtstest;
grant select on sys.USER$ to dtstest;
grant select on SYS.OBJ$ to dtstest;
grant select on SYS.COL$ to dtstest;
grant select on SYS.IND$ to dtstest;
grant select on SYS.ICOL$ to dtstest;
grant select on SYS.CDEF$ to dtstest;
grant select on SYS.CCOL$ to dtstest;
grant select on SYS.TABPART$ to dtstest;
grant select on SYS.TABSUBPART$ to dtstest;
grant select on SYS.TABCOMPART$ to dtstest;
grant select on gv_$listener_network to dtstest;

# The following sample statements show you how to grant permissions on the PDB and CDB to a database account named dtstest.
# Grant permissions on the PDB:
create user dtstest IDENTIFIED BY rdsdt_dtsacct;
grant create  session to dtstest;
grant connect  to dtstest;
grant resource to dtstest;
grant select on  all_objects to dtstest;
grant select on  all_tab_cols to dtstest;
grant select on  dba_registry to dtstest;
grant select any table to dtstest;
grant select any transaction to dtstest;
-- v$log privileges
grant select on v_$log to dtstest;
-- v$logfile privileges
grant select on v_$logfile to dtstest;
-- v$archived_log privileges
grant select on v_$archived_log to dtstest;
-- v$parameter privileges
grant select on v_$parameter to dtstest;
-- v$database privileges
grant select on v_$database to dtstest;
-- v$active_instances privileges
grant select on v_$active_instances to dtstest;
-- v$instance privileges
grant select on v_$instance to dtstest;
-- V$PDBS privileges
grant select on V_$PDBS to dtstest;
grant select on sys.USER$ to dtstest;
grant select on SYS.OBJ$ to dtstest;
grant select on SYS.COL$ to dtstest;
grant select on SYS.IND$ to dtstest;
grant select on SYS.ICOL$ to dtstest;
grant select on SYS.CDEF$ to dtstest;
grant select on SYS.CCOL$ to dtstest;
grant select on SYS.TABPART$ to dtstest;
grant select on SYS.TABSUBPART$ to dtstest;
grant select on SYS.TABCOMPART$ to dtstest;

# Grant permissions on the CDB:
create user dtstest IDENTIFIED BY rdsdt_dtsacct;
grant create   session to dtstest;
grant LOGMINING TO dtstest;
-- v$logmnr_contents privileges
grant select on v_$logmnr_contents to dtstest;

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 an instance type based on the deployment of the source database. In this example, select User-Created Database with Public IP Address. Note If you select other instance types, you must deploy the network environment for the source database. For more information, see Preparation overview.
   	Instance Region	If the instance type is set to User-Created Database with Public IP Address, you do not need to specify the instance region. Note If a whitelist is configured for the self-managed Oracle database, you must add the CIDR blocks of DTS servers to the whitelist of the database. You can click Get IP Address Segment of DTS next to Instance Region to obtain the CIDR blocks of DTS servers.
   	Database Type	Select Oracle.
   	Hostname or IP Address	Enter the endpoint that is used to connect to the self-managed Oracle database. In this example, enter the public IP address.
   	Port Number	Enter the service port number of the self-managed Oracle database. The port must be accessible over the Internet. The default port number is 1521.
   	Instance Type	Non-RAC Instance: If you select this option, you must specify the SID parameter. RAC Instance: If you select this option, you must specify the Service Name parameter.
   	Database Account	Enter the account of the self-managed Oracle database. For more information about the permissions that are required for the account, see Before you begin.
   	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 PolarDB.
   	Instance Region	Select the region where the destination PolarDB for MySQL cluster resides.
   	PolarDB Instance ID	Select the ID of the destination PolarDB for MySQL cluster.
   	Database Account	Enter the database account of the destination PolarDB for MySQL cluster. For more information about the permissions that are required for the account, see Before you begin.
   	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 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 In this step, DTS adds the CIDR blocks of DTS servers to the whitelist of the destination PolarDB for MySQL cluster. This ensures that DTS servers can connect to the destination cluster.
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, do not write data to the source database during full 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. After an object is migrated to the destination RDS instance, the name of the object remains the same as that in the self-managed Oracle database. You can use the object name mapping feature to change the names of the objects that are migrated to the destination RDS instance. For more information, see Object name mapping.
   Specify whether to rename object names	You can use the object name mapping feature to change the names of 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.
   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 destination PolarDB for MySQL cluster.

What to do next

The database accounts that are used for data migration have the read and write permissions. After data migration is complete, you must delete the accounts of both the self-managed Oracle database and the PolarDB for MySQL cluster to ensure database security.

More information

DTS supports reverse data transmission when you migrate data from a self-managed Oracle database to a PolarDB for MySQL cluster. You can use this feature to synchronize data changes from the PolarDB for MySQL cluster to the self-managed Oracle database. To do this, submit a ticket.