This topic describes how to migrate data from a user-created Oracle database to a PolarDB for MySQL cluster by using Data Transmission Service (DTS). DTS supports schema migration, full data migration, and incremental data migration. When you migrate data from a user-created Oracle database, you can select all of the supported migration types to ensure service continuity.

Prerequisites

  • The version of the user-created 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 user-created Oracle database. For more information, see Supplemental Logging.
  • The user-created 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 used storage space of the user-created Oracle database.

Precautions

  • DTS uses read and write resources of the source and destination databases during full data migration. This may increase the database load. 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 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 usage of the source and destination databases is less than 30%.
  • The source database must have PRIMARY KEY or UNIQUE constraints and all fields must be unique. Otherwise, duplicate data may exist in the destination database.
  • 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 avoid name conflicts in the destination database, you can rename 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 Database management.

Billing

Migration type Instance configurations Internet traffic
Schema migration and full data migration Free of charge. Charged only when data is migrated from Alibaba Cloud over the Internet. For more information, see Pricing.
Incremental data migration Charged. For more information, see Pricing.

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 user-created Oracle database to the destination database in the PolarDB for MySQL cluster.

  • Incremental data migration

    DTS retrieves redo log files from the user-created Oracle database. Then, DTS synchronizes incremental data from the user-created 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 the user-created Oracle database to the destination 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.

Note If you have created a database account and the account has the permissions that are listed in the following table, skip this step.
Database Schema migration Full data migration Incremental data migration
User-created Oracle database The owner permission on schemas The owner permission on schemas DBA
PolarDB for MySQL cluster The owner permission on schemas The owner permission on schemas The owner permission on schemas

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

Notice If you need to migrate incremental data from an Oracle database but the DBA permission cannot be granted to the database account, you can grant fine-grained permissions to the account. The following sample statements show you how to grant specific permissions to an Oracle database account.
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_$listener_network to dtstest;
#The following sample statements show you how to grant permissions on the pluggable database (PDB) and container database (CDB) to a database account named dtstest.
#Grant permissions on the PDB:
create user dtstest IDENTIFIED BY rdsdt_dtsacct;
grant create  session to dtstest;
grant connect  to dtstest;
grant resource to dtstest;
grant select on  all_objects to dtstest;
grant select on  all_tab_cols to dtstest;
grant select on  dba_registry to dtstest;
grant select any table to dtstest;
grant select any transaction to dtstest;
-- v$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.
    Select a region
  4. In the upper-right corner of the page, click Create Migration Task.
  5. Configure the source and destination databases.
    Migrate data from a user-created Oracle database to a PolarDB for MySQL cluster
    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 where the source database is deployed. In this example, select User-Created Database with Public IP Address.
    Note If you select other instance types, you must prepare the environment that is required 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 user-created 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 user-created Oracle database. In this example, enter the public IP address.
    Port Number Enter the service port number of the user-created 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.
    • RAC Instance: If you select this option, you must specify the Service Name.
    Database Account Enter the account of the user-created 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 source 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 destination 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 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 objects to be migrated.
    Select the migration types and objects to be migrated
    Parameter Description
    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.
    Notice 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.
    Objects

    Select objects from the Available section and click the Right arrow icon to move the objects to the Selected section.

    Notice
    • You can select columns, tables, or databases 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 names of the objects that are migrated to the destination database by using the object name mapping feature. For more information about how to use this feature, 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. A data migration task can be started only if it passes the precheck.
    • If the task fails to pass the precheck, click the Info icon icon next to each failed item to view details. Troubleshoot the issues based on the causes and perform 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 a data migration task. Otherwise, data migrated to the destination database will be incomplete. Wait until the data migration task automatically stops.

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

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

      Notice 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 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. After the status of incremental data migration changes to The migration task is not delayed, manually stop the migration task.Stop an incremental data 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 user-created 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 user-created 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 user-created Oracle database. To do this, submit a ticket.