Create an active-active disaster recovery project in OceanBase database Community Edition

OceanBase Migration Service (OMS) Community Edition allows you to migrate data between the same type of tenants in OceanBase Database across regions and create active-active disaster recovery projects.

Background

As more users apply OMS Community Edition in data migration, OMS Community Edition must adapt to increasingly diverse scenarios. In addition to single-region data migration and data synchronization, OMS Community Edition supports data migration across regions and active-active data synchronization between remote cities.

OMS Community Edition supports the following active-active disaster recovery scenarios:

• Local data migration and synchronization

• Local primary/standby disaster recovery

• Local active-active disaster recovery

• Remote data migration and synchronization

• Remote primary/standby disaster recovery

• Remote active-active disaster recovery

Primary/standby disaster recovery is common in scenarios with data disaster recovery requirements. You can create a real-time synchronization link between the primary and standby IDCs based on OMS Community Edition. When the primary IDC encounters disasters or downtime, business can be switched to the standby IDC to avoid business interruption.

However, primary/standby disaster recovery causes a waste of resources in the standby IDC. Therefore, OMS Community Edition provides an active-active solution to allow two IDCs to share business traffic.

When you migrate data between tenants of OceanBase Database in an active-active disaster recovery scenario, no forward switchover is performed, and you can enable DDL parameters only for one link.

Prerequisites

• You have created a corresponding schema in the destination tenant of OceanBase Database. OMS Community Edition allows you to migrate tables and columns. Therefore, you must create a corresponding schema in the destination database before migration.

• You have created dedicated database users for data migration in the source and destination OceanBase databases, and granted corresponding privileges to the users. For more information, see Create a database user.

Limits

• OMS Community Edition V3.2.0 and later versions allow you to create active-active disaster recovery links. However, you can migrate only tables with primary keys (including tables that contain the pk and not null uk fields) through active-active disaster recovery links.

• When you create an active-active disaster recovery link, you cannot select reverse incremental migration.

• If you enable DDL operations for incremental data migration, the drop index command is executed on all indexes, which may cause index loss in the destination database.

• You can migrate multiple schemas in a data migration project. The migration granularity ranges from a table to a tenant.

• You can migrate data from OceanBase Database V2.1.0 or later versions. The source and destination tenants can be created in different versions of OceanBase Database.

• If the character set used by the source database is UTF-8, we recommend that you use UTF-8 or a greater character set for the destination database.

• When you migrate data from OceanBase Database V1.4.x, OMS Community Edition does not support primary keys that contain data of the FLOAT or DOUBLE type.

• You must create a forward link and a reverse link to form an active-active disaster recovery link, which does not support triggers.

• You can enable synchronization of DDL operations for incremental migration in either the forward or reverse link.

• In an active-active disaster recovery project in OceanBase Database, when the database is of a version earlier than V3.2.x and contains a multi-partition table that has global unique indexes, if you update the value of a partitioning key of the table, data may be lost during migration.

Create a forward link

1. Create a data migration project.

   1. Log on to the OMS Community Edition console.

   2. In the left-side navigation pane, click Data Migration.

   3. On the Data Migration page, click Create Migration Project in the upper-right corner.

2. On the Select Source and Destination page, specify related parameters.

   Parameter	Description
   Migration Project Name	It can contain Chinese characters, digits, and letters but must not exceed 64 characters in length.
   Tag	Click the field and select a tag from the drop-down list. You can also click Manage Tags to create, modify, or delete tags. For more information, see Use tags to manage data migration projects.
   Source	If you have created an OceanBase data source, select it from the drop-down list. If you have not created a data source, click Add Data Source in the drop-down list, and add a data source in the dialog box that appears on the right. For more information, see Add an OceanBase Community Edition data source.
   Destination	If you have created an OceanBase data source, select it from the drop-down list. If you have not created a data source, click Add Data Source in the drop-down list, and add a data source in the dialog box that appears on the right.
   Scenarios	Two scenarios are available: Data Migration and Active-Active Disaster Recovery . Select Active-Active Disaster Recovery . Notice: The source and destination data sources must be the same type of tenants in OceanBase Database. The source and destination nodes must belong to different regions.

3. Click Next.

4. In the dialog box that appears, click OK.

   Note that this project supports only tables with a primary key or a non-null unique index and other tables are automatically filtered out.

5. On the Select Migration Type page, specify related parameters.

   Migration types available for the forward link include Schema Migration, Full Migration, Incremental Synchronization, and Full Verification.

   Migration type	Limits
   Full Migration	If you select Full Migration , we recommend that you collect the statistics of the source OceanBase database before the data migration.
   Incremental Synchronization	Options available for Incremental Synchronization include DML for Data Change and DDL for Schema Change . The DML operations supported include Insert, Delete, and Update. You can select the operations based on your business needs. You can select the operations based on your business needs. For more information, see Supported DDL operations for incremental migration and limits. Limits on using Incremental Synchronization : You can enable synchronization of DDL operations for incremental migration in either the forward or reverse link. If you select DDL for Schema Change , when you perform a DDL operation for incremental migration that is not supported by OMS Community Edition in the source database, data migration may be interrupted. If you do not select DDL for Schema Change , for DDL operations on tables in the migration link, perform these operations in the destination database first. Otherwise, data migration may be interrupted.
   Full Verification	If you select Full Verification , we recommend that you collect the statistics of both the source and destination OceanBase databases before full verification. If you select Incremental Synchronization but do not select all DML operations in the DML for Data Change section, you cannot select Full Verification .

6. (Optional) Click Next.

   Specify related information for the source OceanBase database.

   • For incremental synchronization, specify the ConfigUrl, username, and password.

   • For schema migration, specify the username and password.

   • For the migration of a table without a unique key, specify the password of _OCEANBASE_INNER_DRC_USER.

   If you select Scheme Migration or Incremental Synchronization but no related parameters are configured for the data source of the source database, the More about Data Sources dialog box appears, prompting you to configure related parameters. For more information, see Add an OceanBase Community Edition data source.

   After you set the required parameters, click Test Connectivity. After the test succeeds, click Save.

7. Click Next. On the Select Objects page, select the migration objects and migration scope.

   Select Specify Objects or Match Rules. If you select DDL for Schema Change, only the Match Rules option is available.

   • Select Specify Objects . Then, select the objects to be migrated on the left, and click > to add them to the list on the right. You can select tables and views of one or more databases as the migration objects.

     Notice

     • The name of a table to be migrated, as well as the names of columns in the table, must not contain Chinese characters.

     • If the database or table name contains a double dollar sign ($$), you cannot create the migration project.

     When you migrate data between OceanBase databases, OMS Community Edition allows you to import objects through text, rename object names, set row filters, view column information, and remove a single object or all objects to be migrated.

     Operation	Steps
     Import Objects	In the list on the right of the Specify Migration Scope section, click Import Objects in the upper-right corner. In the dialog box that appears, click OK. Notice: This operation will overwrite previous selections. Proceed with caution. In the Import Migration Object dialog box, import the objects to be migrated. You can import a CSV file to perform operations such as rename database tables or set row filters. For more information, see Download and import the settings of migration objects. Click Validate. After the validation succeeds, click OK.
     Rename	In the list on the right of the Specify Migration Scope section, hover the pointer over the target object. Click Rename. Enter a new name and click OK.
     Settings	OMS Community Edition allows you to set WHERE conditions to filter data by row and view column information. In the list on the right of the Specify Migration Scope section, hover the pointer over the target object. Click Settings. In the Settings dialog box, enter a WHERE clause of a standard SQL statement to configure row-based filtering. Only the data meeting the WHERE condition is synchronized to the destination data source, thereby filtering data by row. Notice: Add an escape character (`) for column names. Example: `col`. If row-based filtering with the WHERE clause is enabled, right-trim is forcibly performed on data of the CHAR or VARCHAR type, which may cause an inaccurate comparison of the VARCHAR data. Proceed with caution. Click OK. You can also view column information of the migration object in the View Column section.
     Remove/Remove All	OMS Community Edition allows you to remove a single migration object or all migration objects. Remove a single migration object In the list on the right of the Specify Migration Scope section, hover the pointer over the target object, and click Remove. The migration object is removed. Remove all migration objects In the list on the right of the Specify Migration Scope section, click Remove All in the upper-right corner. In the dialog box that appears, click OK to remove all migration objects.

   • Select Match Rules . For more information, see Configure matching rules for migration objects.

8. Click Next. On the Migration Options page, specify the following parameters.

   Category	Parameter	Description
   Basic Settings	Concurrency for Full Migration	The value can be Smooth, Normal, or Fast. The quantity of resources to be consumed by a full data migration task varies based on the migration performance. You can also modify the configurations of the Checker-Full component to customize the concurrency. Notice To enable this feature, select Full Migration on the Select Migration Type page.
   Basic Settings	Full Verification Concurrency	The value can be Smooth , Normal , or Fast . Different quantities of resources of the source and destination databases are consumed at different concurrencies. You can also modify the configurations of the Checker-Verify component to customize the concurrency.
   Basic Settings	Incremental Record Retention Time	The duration that incremental parsed files are cached in OMS Community Edition. A longer retention period indicates more disk space occupied by the Store component of OMS Community Edition.
   Advanced Settings	Whether to Allow Destination Table to Be Not Empty During Full Migration	If destination tables are allowed to be not empty during full migration, full verification is performed in IN mode, and you do not need to deselect Full Verification. Notice: To enable this feature, select Full Migration on the Select Migration Type page.
   Advanced Settings	Whether to Allow Post-indexing	You can specify whether to create indexes after the full migration is completed. Post-indexing can shorten the time of full migration. Notice: To enable this feature, select both Schema Migration and Full Migration on the Select Migration Type page. Only non-unique key indexes can be created after the migration is completed.

9. Click Precheck to start a precheck on the data migration project.

   During the precheck, OMS Community Edition checks the read and write privileges of the database users and the network connections of the databases. The data migration project can be started only after it passes all check items. If the precheck fails, identify the cause, fix the problem, and run the precheck again until it succeeds.

10. Click Start Task to start tasks of the project such as schema migration and full migration.

    If you do not need to start the project now, click Save to go to the details page of the data migration project. You can start the project later as needed. For more information about project details, see View details of a data migration project.

Create a reverse link

You can create a reverse link only after the schema migration task on the forward link is completed.

1. On the Data Migration page, click Create Migration Project in the upper-right corner.

2. On the Select Source and Destination page, specify related parameters.

3. Click Next.

4. In the dialog box that appears, click OK.

   Note that this project supports only tables with a primary key or a non-null unique index and other tables are automatically filtered out.

5. On the Select Migration Type page, specify related parameters.

   For the reverse link, set Migration Type to Incremental Synchronization.

   Notice

   You can enable synchronization of DDL operations for incremental migration in either the forward or reverse link.

6. (Optional) Click Next.

   For incremental synchronization, specify the ConfigUrl, username, and password of the source database. For the migration of a table without a unique key, you need to specify the password of _OCEANBASE_INNER_DRC_USER.

   If no related parameters are configured for the source database, the More about Data Sources dialog box appears, prompting you to configure related parameters. For more information, see Add an OceanBase Community Edition data source. After you set the required parameters, click Test Connectivity. After the test succeeds, click Save.

7. Click Next. On the Select Objects page, select the migration objects and migration scope.

   When you create a reverse link, OMS Community Edition also allows you to import objects through text, rename object names, set row filters, view column information, and remove one or all objects to be migrated. For more information, see the section that describes how to create a forward link.

8. Click Next. On the Migration Options page, specify the following parameters.

9. Click Precheck to start a precheck on the data migration project.

10. Click Start Project.