This topic describes how to migrate data from a self-managed Oracle database to a PolarDB for Oracle cluster by using Data Transmission Service (DTS).

Prerequisites

  • The schema of the source Oracle database is migrated to the destination PolarDB for Oracle cluster by using Advanced Database & Application Migration (ADAM). For more information, see steps in Migrate the schema of a self-managed Oracle database to a PolarDB for Oracle cluster.
  • The source Oracle database and the destination PolarDB for Oracle cluster are created.
    Note
  • 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.
  • 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.

Limits

Category Description
Limits on the source database
  • The server to which the source database belongs must have sufficient outbound bandwidth. Otherwise, the data migration speed decreases.
  • If the source database is connected over Express Connect, you must specify a virtual IP address (VIP) for the database when you configure the source database information.
  • If the source database is an Oracle RAC database hosted on Elastic Compute Service (ECS) or connected over Express Connect, VPN Gateway, Smart Access Gateway, Database Gateway, or Cloud Enterprise Network (CEN), you can use a single VIP rather than a Single Client Access Name (SCAN) IP address when you configure the source database information. After you specify the VIP, node failover is not supported for the Oracle RAC database.
  • Requirements for the objects to migrate:
    • The tables to migrate must have PRIMARY KEY or UNIQUE constraints and all fields must be unique. Otherwise, the destination database may contain duplicate data records.
    • If the version number of your Oracle database is 12c or later, the names of the tables to migrate cannot exceed 30 bytes in length.
    • If you select tables as the objects to migrate and you want to edit the tables (such as renaming tables or columns) in the destination database, up to 1,000 tables can be migrated in a single data migration task. If you run a task to migrate more than 1,000 tables, a request error occurs. In this case, we recommend that you split the tables and configure multiple tasks to migrate the tables, or configure a task to migrate the entire database.
  • If you want to migrate incremental data, you must make sure that the following requirements are met:
    • The redo logging and archive logging must be enabled.

    • For an incremental data migration task, redo logs and archive logs of the source database must be stored for more than 24 hours. For a full data and incremental data migration task, redo logs and archive logs of the source database must be stored for at least seven days. After the full data migration is completed, you can set the retention period to more than 24 hours. Otherwise, Data Transmission Service (DTS) may fail to obtain the redo logs and archive logs, and the task may fail. In exceptional circumstances, data inconsistency or loss may occur. Make sure that you set the retention period of redo logs and archive logs in accordance with the preceding requirements. Otherwise, the Service Level Agreement (SLA) of DTS does not ensure service reliability and performance.

  • Limits on operations:
    • During schema migration and full data migration, do not perform DDL operations to change the schemas of databases or tables. Otherwise, the data migration task fails.
    • If you perform only full data migration, do not write data to the source database during data migration. Otherwise, data inconsistency between the source and destination databases occurs. To ensure data consistency, we recommend that you select schema migration, full data migration, and incremental data migration as the migration types.
    • During data migration, do not update LONGTEXT fields. Otherwise, the data migration task fails.
Other limits
  • 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. During full data migration, DTS uses read and write resources of the source and destination databases. This may increase the loads of the database servers.
  • During full data migration, concurrent INSERT operations cause fragmentation in the tables of the destination database. After full data migration is completed, the tablespace of the destination database is larger than that of the source database.
  • DTS attempts to resume data migration tasks that failed within the last seven days. Before you switch workloads over to the destination instance, stop or release the data migration task. You can also execute the REVOKE statement to revoke write permissions from the accounts used by DTS to access the destination instance. Otherwise, the data in the source database overwrites the data in the destination instance after the task is resumed.

Billing

Migration type Task configuration fee Internet traffic fee
Full data migration Free of charge. Charged only when data is migrated from Alibaba Cloud over the Internet. For more information, see Billing overview.
Incremental data migration Charged. For more information, see Billing overview.

Migration types

Migration type Description
Full data migration DTS migrates the historical data of required objects from the self-managed Oracle database to the destination PolarDB for Oracle cluster.
Note In this scenario, DTS does not support triggers. We recommend that you delete the triggers of the source database to prevent data inconsistency caused by triggers. For more information, see Configure a data synchronization task for a source database that contains a trigger.
Incremental data migration DTS retrieves redo log files from the self-managed Oracle database. Then, DTS migrates incremental data from the self-managed Oracle database to the destination PolarDB for Oracle cluster.

Incremental data migration allows you to ensure service continuity when you migrate data from an Oracle database to a PolarDB for Oracle cluster.

SQL operations that can be migrated

Operation type SQL statement
DML INSERT, UPDATE, and DELETE
DDL
  • CREATE TABLE
    Note If a CREATE TABLE statement contains partitioning clauses, subpartitioning clauses, or functions, DTS does not migrate the statement. In addition, DTS does not migrate the CREATE TABLE AS SELECT statements.
  • ALTER TABLE, including ADD COLUMN, ADD INDEX, DROP COLUMN, DROP INDEX, MODIFY COLUMN, and RENAME COLUMN
  • DROP TABLE
  • RENAME TABLE, TRUNCATE TABLE, and CREATE INDEX

Preparations

Log on to the self-managed Oracle database, create an account that you want to use to collect data, and then grant permissions to the account.

Note If you have created an account that is granted the permissions listed in the following table, you can skip this step.
Database Full data migration Incremental data migration
Self-managed Oracle database Permissions of the schema owner Database administrator (DBA)
PolarDB for Oracle cluster Permissions of the schema owner

To create a database account and grant permissions to the database account, perform the following operations:

Important If you need to migrate incremental data from an Oracle database but the database administrator (DBA) permissions cannot be granted to the database account, you can enable archive logging and supplemental logging, and grant fine-grained permissions to the account.

  1. Enable archive logging and supplemental logging.
    Type Procedure
    Archive logging Execute the following statements to enable archive logging:
    shutdown immediate;
startup mount;
alter database archivelog;
alter database open;
archive log list;
    Supplemental logging Enable supplemental logging at the database or table level based on your business requirements.
    Note You can enable database-level supplemental logging to ensure the stability of Data Transmission Service (DTS) tasks. You can enable table-level supplemental logging to reduce the disk usage of the source Oracle database.
    • Enable database-level supplemental logging
      1. Execute the following statement to enable minimal supplemental logging:
        alter database add supplemental log data;
      2. Execute the following statement to enable primary key and unique key supplemental logging at the database level:
        alter database add supplemental log data (primary key,unique index) columns;
    • Enable table-level supplemental logging
      1. Execute the following statement to enable minimal supplemental logging:
        alter database add supplemental log data;
      2. Enable table-level supplemental logging by using one of the following methods:
        • Enable primary key supplemental logging at the table level
          alter table table_name add supplemental log data (primary key) columns;
        • Enable table-level supplemental logging for all columns
          alter table tb_name add supplemental log data (all) columns;
    Force logging Execute the following statement to enable force logging:
    alter database force logging;
  2. Grant fine-grained permissions to an Oracle database account. 
    # Create a database account named 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;
grant execute on sys.dbms_logmnr to rdsdt_dtsacct;
grant select on V_$LOGMNR_LOGS to rdsdt_dtsacct;
grant select on  all_objects to rdsdt_dtsacct;
grant select on  all_tab_cols to rdsdt_dtsacct;
grant select on  dba_registry to rdsdt_dtsacct;
grant select any table to rdsdt_dtsacct;
grant select any transaction to rdsdt_dtsacct;
-- v$log privileges
grant select on v_$log to rdsdt_dtsacct;
-- v$logfile privileges
grant select on v_$logfile to rdsdt_dtsacct;
-- v$archived_log privileges
grant select on v_$archived_log to rdsdt_dtsacct;
-- v$parameter privileges
grant select on v_$parameter to rdsdt_dtsacct;
-- v$database privileges
grant select on v_$database to rdsdt_dtsacct;
-- v$active_instances privileges
grant select on v_$active_instances to rdsdt_dtsacct;
-- v$instance privileges
grant select on v_$instance to rdsdt_dtsacct;
-- v$logmnr_contents privileges
grant select on v_$logmnr_contents to rdsdt_dtsacct;
-- system tables
grant select on sys.USER$ to rdsdt_dtsacct;
grant select on SYS.OBJ$ to rdsdt_dtsacct;
grant select on SYS.COL$ to rdsdt_dtsacct;
grant select on SYS.IND$ to rdsdt_dtsacct;
grant select on SYS.ICOL$ to rdsdt_dtsacct;
grant select on SYS.CDEF$ to rdsdt_dtsacct;
grant select on SYS.CCOL$ to rdsdt_dtsacct;
grant select on SYS.TABPART$ to rdsdt_dtsacct;
grant select on SYS.TABSUBPART$ to rdsdt_dtsacct;
grant select on SYS.TABCOMPART$ to rdsdt_dtsacct;
grant select_catalog_role TO rdsdt_dtsacct;

    # Switch to the pluggable database (PDB). Create a database account named rdsdt_dtsacct and grant permissions to the account.
ALTER SESSION SET container = ORCLPDB1;
create user rdsdt_dtsacct IDENTIFIED BY rdsdt_dtsacct;
grant create  session to rdsdt_dtsacct;
grant connect  to rdsdt_dtsacct;
grant resource to rdsdt_dtsacct;
grant execute on sys.dbms_logmnr to rdsdt_dtsacct;
grant select on  all_objects to rdsdt_dtsacct;
grant select on  all_tab_cols to rdsdt_dtsacct;
grant select on  dba_registry to rdsdt_dtsacct;
grant select any table to rdsdt_dtsacct;
grant select any transaction to rdsdt_dtsacct;
-- v$log privileges
grant select on v_$log to rdsdt_dtsacct;
-- v$logfile privileges
grant select on v_$logfile to rdsdt_dtsacct;
-- v$archived_log privileges
grant select on v_$archived_log to rdsdt_dtsacct;
-- v$parameter privileges
grant select on v_$parameter to rdsdt_dtsacct;
-- v$database privileges
grant select on v_$database to rdsdt_dtsacct;
-- v$active_instances privileges
grant select on v_$active_instances to rdsdt_dtsacct;
-- v$instance privileges
grant select on v_$instance to rdsdt_dtsacct;
-- v$logmnr_contents privileges
grant select on v_$logmnr_contents to rdsdt_dtsacct;
grant select on sys.USER$ to rdsdt_dtsacct;
grant select on SYS.OBJ$ to rdsdt_dtsacct;
grant select on SYS.COL$ to rdsdt_dtsacct;
grant select on SYS.IND$ to rdsdt_dtsacct;
grant select on SYS.ICOL$ to rdsdt_dtsacct;
grant select on SYS.CDEF$ to rdsdt_dtsacct;
grant select on SYS.CCOL$ to rdsdt_dtsacct;
grant select on SYS.TABPART$ to rdsdt_dtsacct;
grant select on SYS.TABSUBPART$ to rdsdt_dtsacct;
grant select on SYS.TABCOMPART$ to rdsdt_dtsacct;
-- V$PDBS privileges
grant select on V_$PDBS to rdsdt_dtsacct;
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;

# Switch to the CDB$ROOT, which is the root container of the container database (CDB). Create a database account and grant permissions to the account.
ALTER SESSION SET container = CDB$ROOT;
# Create a database account named rdsdt_dtsacct and grant permissions to the account. You must modify the default parameters of the Oracle database. 
alter session set "_ORACLE_SCRIPT"=true;
create user rdsdt_dtsacct IDENTIFIED BY rdsdt_dtsacct;
grant create session to rdsdt_dtsacct;
grant connect to rdsdt_dtsacct;
grant select on v_$logmnr_contents to rdsdt_dtsacct;
grant LOGMINING TO rdsdt_dtsacct;
grant EXECUTE_CATALOG_ROLE to rdsdt_dtsacct;
grant execute on sys.dbms_logmnr to rdsdt_dtsacct;
grant select_catalog_role TO rdsdt_dtsacct;

    # Create a database account named 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;
grant select on V_$LOGMNR_LOGS to rdsdt_dtsacct;
grant select on  all_objects to rdsdt_dtsacct;
grant select on  all_tab_cols to rdsdt_dtsacct;
grant select on  dba_registry to rdsdt_dtsacct;
grant select any table to rdsdt_dtsacct;
grant select any transaction to rdsdt_dtsacct;
grant select on v$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;
-- v$log privileges
grant select on v_$log to rdsdt_dtsacct;
-- v$logfile privileges
grant select on v_$logfile to rdsdt_dtsacct;
-- v$archived_log privileges
grant select on v_$archived_log to rdsdt_dtsacct;
-- v$parameter privileges
grant select on v_$parameter to rdsdt_dtsacct;
-- v$database privileges
grant select on v_$database to rdsdt_dtsacct;
-- v$active_instances privileges
grant select on v_$active_instances to rdsdt_dtsacct;
-- v$instance privileges
grant select on v_$instance to rdsdt_dtsacct;
-- v$logmnr_contents privileges
grant select on v_$logmnr_contents to rdsdt_dtsacct;
grant select on sys.USER$ to rdsdt_dtsacct;
grant select on SYS.OBJ$ to rdsdt_dtsacct;
grant select on SYS.COL$ to rdsdt_dtsacct;
grant select on SYS.IND$ to rdsdt_dtsacct;
grant select on SYS.ICOL$ to rdsdt_dtsacct;
grant select on SYS.CDEF$ to rdsdt_dtsacct;
grant select on SYS.CCOL$ to rdsdt_dtsacct;
grant select on SYS.TABPART$ to rdsdt_dtsacct;
grant select on SYS.TABSUBPART$ to rdsdt_dtsacct;
grant select on SYS.TABCOMPART$ to rdsdt_dtsacct;
grant LOGMINING TO rdsdt_dtsacct;
grant EXECUTE_CATALOG_ROLE to rdsdt_dtsacct;
grant execute on sys.dbms_logmnr to rdsdt_dtsacct;
grant select_catalog_role TO rdsdt_dtsacct;

Procedure

  1. Go to the Data Migration page of the new DTS console.
    Note You can also log on to the Data Management (DMS) console. In the top navigation bar, click DTS.. In the left-side navigation pane, click Data Migration.
  2. In the top navigation bar, select the region where the data migration instance resides.
    Select a region
  3. Click Create Task. On the page that appears, configure the source and destination databases.
    Warning After you select the source and destination instances, we recommend that you read the limits displayed at the top of the page. This helps you create and run the data migration task.
    Section Parameter Description
    N/A Task Name

    DTS automatically generates a task name. We recommend that you specify an informative name to identify the task. You do not need to use a unique task name.

    Source Database Database Type Select Oracle.
    Access Method Select an access method based on the deployment of the source database. In this example, Public IP Address is selected.
    Note If you select other access methods, you must set up the environment that is required for the self-managed Oracle database. For more information, see Preparation overview.
    Instance Region Select the region where the source Oracle database resides.
    Hostname or IP address The IP address that is used to access the self-managed Oracle database.
    Port Number The service port number of the self-managed Oracle database. Default value: 1521.
    Note The service port of the self-managed Oracle database must be accessible over the Internet.
    Oracle Type
    • If you select Non-RAC Instance, you must specify the SID parameter.
    • If you select RAC or PDB Instance, you must specify the Service Name parameter.
    In this example, Non-RAC Instance is selected.
    Database Account The account of the source Oracle database. For more information about the permissions that are required for the account, see Preparations.
    Database Password

    Enter the password of the database account.

    Destination Database Database Type Select PolarDB for Oracle.
    Access Method Select Public IP Address.
    Instance Region Select the region in which the destination PolarDB for Oracle cluster resides.
    Data Sources
    • If you select Single Data Source, you must specify the Domain Name or IP Address and Port Number parameters of the primary node in the destination PolarDB for Oracle cluster.
    • If you select Multiple Data Sources, you must specify the IP addresses and port numbers of multiple nodes, including the primary node, in the destination PolarDB for Oracle cluster in the IP:Port of Data Sources field.
      Note If you select Multiple Data Sources and specify the IP:Port of Data Sources parameter, DTS can automatically switch to a new primary node in the PolarDB for Oracle cluster during primary/secondary switchover. This is suitable for scenarios such as disaster recovery.
    In this example, Single Data Source is selected.
    Domain Name or IP Address The IP address of the primary node in the destination PolarDB for Oracle cluster.
    Note You can run the ping command on your computer to obtain the IP address that is used to access the destination PolarDB for Oracle cluster.
    Port Number The service port number of the destination database. Default value: 1521.
    IP:Port of Data Sources The addresses of multiple nodes, including the primary node, of the destination PolarDB for Oracle cluster in the <IP address>:<Port number> format. Separate multiple node addresses with commas (,).
    Database Name The name of the destination database in the PolarDB for Oracle cluster.
    Database Account The database account of the destination PolarDB for Oracle cluster. For information about the permissions that are required for the account, see Preparations.
    Database Password

    Enter the password of the database account.

  4. If a whitelist is configured for your self-managed database, you must add the CIDR blocks of DTS servers to the whitelist. Then, click Test Connectivity and Proceed.
    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, Alibaba Cloud 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: enhancing the security of your username and password, limiting the ports that are exposed, authenticating API calls, regularly checking the whitelist or ECS security group rules and forbidding unauthorized CIDR blocks, or connecting the database to DTS by using Express Connect, VPN Gateway, or Smart Access Gateway.
    • After the DTS task is complete or released, we recommend that you manually detect and remove the added CIDR blocks from the whitelist of the database, Alibaba Cloud database instance, or ECS security group rules.
  5. Select objects for the task and configure advanced settings.
    • Basic Settings
      Parameter or setting Description
      Task Stages
      • 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 instance during data migration. This ensures data consistency between the source and destination instances.
      Processing Mode of Conflicting Tables

      • Precheck and Report Errors: checks whether the destination database contains tables that have the same names as tables in the source database. If the source and destination databases do not contain identical table names, the precheck is passed. Otherwise, an error is returned during precheck and the data migration task cannot be started.

        Note You can use the object name mapping feature to rename the tables that are migrated to the destination database. You can use this feature if the source and destination databases contain identical table names and the tables in the destination database cannot be deleted or renamed. For more information, see Map object names .
      • Ignore Errors and Proceed: skips the precheck for identical table names in the source and destination databases.
        Warning If you select Ignore Errors and Proceed, data consistency is not guaranteed and your business may be exposed to potential risks.
        • If the source and destination databases have the same schema, DTS does not migrate data records that have the same primary keys as data records in the destination database.
        • If the source and destination databases have different schemas, only specific columns are migrated or the data migration task fails.
      Select Objects

      Select one or more objects from the Source Objects section and click the Rightwards arrow icon to add the objects to the Selected Objects section.

      Rename Databases and Tables
      Warning In this scenario, the schema of the source database is migrated to the destination database by using ADAM. We recommend that you do not use the object name mapping feature. Otherwise, the data migration task fails.
      Filter data

      You can specify WHERE conditions to filter data. For more information, see Use SQL conditions to filter data.

      Select the SQL operations to be migrated In the Selected Objects section, right-click an object. In the dialog box that appears, select the SQL operations that you want to migrate. For more information, see SQL operations that can be migrated.
    • Advanced Settings
      Parameter Description
      Set Alerts
      Specify whether to set alerts for the data migration task. If the task fails or the migration latency exceeds the threshold, the alert contacts will receive notifications.
      • Select No if you do not want to set alerts.
      • Select Yes to set alerts. In this case, you must also set the alert threshold and alert contacts.
      Retry Time for Failed Connections
      Specify the retry time range for failed connections. Valid values: 10 to 720. Unit: minutes. Default value: 720. We recommend that you set the retry time range to more than 30 minutes. If DTS reconnects to the source and destination databases within the specified time range, DTS resumes the data migration task. Otherwise, the data migration task fails.
      Note
      • If you set different retry time ranges for multiple data migration tasks that have the same source or destination database, the value that is set later takes precedence.
      • When DTS retries a connection, you are charged for the DTS instance. We recommend that you specify the retry time range based on your business requirements. You can also release the DTS instance at your earliest opportunity after the source and destination instances are released.
  6. In the lower part of the page, click Next: Save Task Settings and Precheck.
    Note
    • Before you can start the data migration task, DTS performs a precheck. 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 Info icon 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.
  7. Wait until the Success Rate becomes 100%. Then, click Next: Purchase Instance.
  8. On the Purchase Instance page, specify the Instance Class parameter for the data migration instance. The following table describes the parameter.
    Section Parameter Description
    Parameters Instance Class

    DTS provides several instance classes that have different performance in migration speed. You can select an instance class based on your business scenario. For more information, see Specifications of data migration instances.

  9. Read and select Data Transmission Service (Pay-as-you-go) Service Terms.
  10. Click Buy and Start to start the data migration task. You can view the progress of the task in the task list.