Overview|V4.2.5|OceanBase Migration Service|docs|OceanBase Documentations

OceanBase Migration Service (OMS) provide data migration. You can use OMS to migrate data between OceanBase Database and other data sources in real time.

Background

OMS supports online migration. The server deployed with OMS must be able to connect to both source and destination database instances at the same time. You can start a data migration task simply after you configure the source and destination databases and select the objects to be migrated.

OMS automatically performs all the procedures in a data migration task, replicating the database objects, existing data, or incremental data in the source database (data table) to the destination database (data table). It also ensures the real-time synchronization of incremental data from the source database to the destination database.

Supported migration types

In the following table, OB_MySQL stands for a MySQL-compatible tenant of OceanBase Database, and OB_Oracle stands for an Oracle-compatible tenant of OceanBase Database. For more information about the DDL operations supported in incremental synchronization, see topics in the Yes DDL operations for synchronization and limitations chapter.

Data migration task	Schema migration	Full migration	Incremental synchronization of DML operations	Incremental synchronization of DDL operations	Full verification	Reverse incremental synchronization	Table without a primary key
MySQL -> OB_MySQL	Yes	Yes	Yes	Yes	Yes	Yes	Yes
Oracle -> OB_MySQL	Yes	Yes	Yes	No	Yes	Yes	Yes
TiDB -> OB_MySQL	Yes	Yes	Yes	No	Yes	Yes	No
PostgreSQL -> OB_MySQL	Yes	Yes	Yes	No	Yes	Yes	No
Oracle -> OB_Oracle	Yes	Yes	Yes	Yes	Yes	Yes	Yes
DB2 LUW -> OB_Oracle	Yes	Yes	Yes	Yes	Yes	Yes	No
OB_Oracle -> OB_Oracle	Yes	Yes	Yes	Yes	Yes	Yes	Yes
OB_MySQL -> OB_MySQL	Yes	Yes	Yes	Yes	Yes	Yes	Yes (not supported in active-active disaster recovery scenarios)
OB_Oracle -> Oracle	Yes	Yes	Yes	Yes	Yes	Yes	Yes
OB_Oracle -> MySQL	No	No	Yes	No	No	No	No
OB_MySQL -> MySQL	Yes	Yes	Yes	Yes	Yes	Yes	No
OB_Oracle -> DB2 LUW	Yes	Yes	Yes	Yes	Yes	Yes	No
DB2 LUW -> OB_MySQL	Yes	Yes	Yes	Yes	Yes	Yes	No
OB_MySQL -> DB2 LUW	Yes	Yes	Yes	Yes	Yes	Yes	No

Migration types

Migration type	Description
Schema migration	OMS migrates the definitions of data objects, such as tables, indexes, constraints, comments, and views, from the source database to the destination database. Temporary tables are automatically filtered out. If the source database is not an OceanBase database, OMS Community Edition performs format conversion and encapsulation based on the syntax definition and standard of the type of the destination tenant of OceanBase Database and then replicates the data to the destination database.
Full migration	OMS migrates the existing data from tables in the source database to the corresponding tables in the destination database. On the Full Migration page, you can view information on the , Table Indexes, and Migration Performance tabs. The status of a full migration task changes to Completed only after the table objects and table indexes are migrated. On the Table Indexes page, you can click View Creation Syntax next to a table to view its index creation syntax. You can combine full migration with incremental synchronization to ensure data consistency between the source and destination databases. If any objects fail to be migrated during full migration, the causes of the failure are displayed.
Incremental synchronization	OMS synchronizes the data that has been changed (added, modified, or deleted) in the source database to the corresponding tables in the destination database. When services continuously write data to the source database, OMS starts the incremental data pull module to pull incremental data from the source instance, parses and encapsulates the incremental data, and then stores the data in OMS. After that, OMS starts the full data migration. After the full data migration task is completed, OMS starts the incremental data replay module to pull incremental data from the incremental data pull module. The incremental data is synchronized to the destination instance after being filtered, mapped, and converted.
Full verification	After the full data migration and incremental data migration are completed, OMS automatically initiates a full data verification task to verify the data tables in the source and destination databases. You can initiate custom data verification tasks during incremental data synchronization. If tables with inconsistent data are detected, you can choose to re-verify all data or only the inconsistent data in the tables.
Forward switchover	Forward switchover is an abstract and standard process of traditional system cutover and does not involve the switchover of application connections. This process includes a series of tasks that are performed by OMS for application switchover in a data migration task. You must make sure that the entire forward switchover process is completed before the application connections are switched over to the destination database. Forward switchover is required for data migration. By performing forward switchover, OMS ensures the completion of forward data migration. You can start the Incr-Sync component for reverse incremental synchronization based on your business needs. The forward switchover process involves the following operations: You must make sure that data migration is completed and wait until forward synchronization is completed. OMS automatically supplements CHECK constraints, FOREIGN KEY constraints, and other objects that are ignored in the schema migration phase when the destination is an Oracle database, an Oracle-compatible tenant of OceanBase Database, or a DB2 LUW database. OMS automatically drops the additional hidden columns and unique indexes that the migration depends on. This operation is required only when you migrate data between an Oracle database and an OceanBase database or between OceanBase databases. For more information, see Mechanisms for handling hidden columns. You need to supplement triggers, functions, stored procedures, and other database objects at the source that are not supported by OMS to the destination. You must disable triggers and FOREIGN KEY constraints in the source database. This operation is required only when the data migration task involves reverse incremental synchronization.
Reverse incremental	In business cutover scenarios, after the migration is completed, you can start an incremental synchronization task in a reverse direction. In other words, you can synchronize data from the destination database to the source database before the business database switchover. In this way, data changes made in the destination database after the switchover are applied to the source business database in real time.

Supported task types

OMS provides the online data migration and real-time incremental data synchronization features. The following task types are supported:

Note

For more information about the version restrictions on data sources, see Limitations.