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.
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:
- User-created Oracle database: CREATE USER and GRANT
- PolarDB for MySQL cluster: Create database accounts 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_$listener_network to dtstest;
#The following sample statements show you how to grant permissions on the pluggable database (PDB) and container database (CDB) to a database account named dtstest. #Grant permissions on the PDB: create user dtstest IDENTIFIED BY rdsdt_dtsacct; grant create session to dtstest; grant connect to dtstest; grant resource to dtstest; grant select on all_objects to dtstest; grant select on all_tab_cols to dtstest; grant select on dba_registry to dtstest; grant select any table to dtstest; grant select any transaction to dtstest; -- v$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
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.