This topic describes how to use OceanBase Migration Service (OMS) to migrate data from a DB2 LUW database to a MySQL-compatible tenant of OceanBase Database, which can be a physical data source, a public cloud OceanBase data source, or a standalone data source.
Prerequisites
You have created dedicated database users in the source DB2 LUW database and the target MySQL-compatible tenant of OceanBase Database for data migration and granted the required privileges to the users.
Keep the logs of the DB2 LUW database for at least one day to prepare for a possible pullback in case of exceptions.
Limitations
Limitations on the source database
Do not perform DDL operations that modify database or table schemas during schema migration or full migration. Otherwise, the data migration task may be interrupted.
DB2 LUW 9.7, 10.1, 10.5, 11.1, and 11.5 for Linux and AIX are supported.
When DB2 LUW 9.7.x serves as the source, DDL synchronization is not supported.
In an ARM CPU architecture, OMS does not support incremental synchronization from a DB2 LUW database to a MySQL-compatible tenant of OceanBase Database.
OMS does not support triggers in the target database. If triggers exist in the target database, the data migration may fail.
Data source identifiers, user accounts, and tags must be globally unique in OMS.
OMS only supports migrating databases, tables, and column objects with ASCII-compliant names that do not contain special characters (spaces, line breaks, or .|"'`()=;/&\).
The following character sets are supported: BINARY, GBK, GB18030, UTF8MB4, UTF-16, and UTF-8. If the UTF-8 character set is used in the source database, we recommend that you use a compatible character set, such as UTF-8 or UTF-16, in the target database to avoid garbled characters.
In reverse increment from a DB2 LUW database to a MySQL-compatible tenant of OceanBase Database, a database name or table name in the source database cannot contain a lowercase letter. Otherwise, the check items of the reverse increment will fail the precheck.
OMS does not support data migration from a DB2 LUW database to a case-sensitive MySQL-compatible tenant of OceanBase Database.
In a task for reverse increment from a DB2 LUW database to a MySQL-compatible tenant of OceanBase Database of a version earlier than V3.2.x, if the source table is a multi-partition table with a global unique index and you update the values of the partition key of the table, data may be lost during migration.
Considerations
If the unique key is of the floating-point format, make sure that the precision of the source table is inconsistent with that of the target table. Otherwise, the full verification will fail.
By default,
lower_table_case_namesis set to1in the target database, and the target database objects are created with lowercase names.If the clocks between nodes or between the client and the server are out of synchronization, the latency may be inaccurate during incremental synchronization or reverse increment.
For example, if the clock is earlier than the standard time, the latency can be negative. If the clock is later than the standard time, the latency can be positive.
Given that DB2 LUW and OceanBase Database adopt heterogeneous database architectures, we recommend that you keep the schema collations of the source and target databases consistent. Otherwise, data inconsistency may be identified during data synchronization or verification.
By default, data sorting in the DB2 LUW database is case-sensitive. Therefore, the schema collation of the MySQL-compatible tenant of OceanBase Database must be set to case-sensitive.
If the source DB2 LUW database uses the utf8bm4 character set and the IDENTITY collation, the collation of the MySQL-compatible tenant of OceanBase Database can be set to utf8mb4_bin.
Check whether the migration precision of OMS for fields of data types such as DECIMAL, FLOAT, and DOUBLE is as expected. If the precision of the target field type is lower than that of the source field type, the value with a higher precision may be truncated. This may result in data inconsistency between the source and target fields.
When DDL synchronization is disabled, if you change the unique index in the target database, you must restart the Incr-Sync component. Otherwise, the data in the source and target databases may be inconsistent.
In multi-table aggregation scenarios:
We recommend that you configure the mappings between the source and target databases by specifying matching rules.
We recommend that you manually create schemas in the target database. If you use OMS to create schemas, skip failed objects in the schema migration step.
A difference between the source and target table schemas may result in data consistency. Some known scenarios are described as follows:
When you manually create a table schema in the target database, if the data types of any columns are not supported by OMS, implicit data type conversion may occur in the target database, which causes inconsistent column types between the source and target databases.
If the length of a column in the target database is shorter than that in the source database, the data of this column may be automatically truncated, which causes data inconsistency between the source and target databases.
If you select only Incremental Synchronization when you create the data migration task, OMS requires that the archive logs in the source database be retained for more than 48 hours.
If you select Full Migration and Incremental Synchronization when you create the data migration task, OMS requires that the archive logs in the source database be retained for at least seven days. Otherwise, the data migration task may fail or the data in the source and target databases may be inconsistent because OMS cannot obtain incremental logs.
If the source and target table objects differ only in capitalization of their names, the data migration result may not be as expected because the object names in the source or target database are case-insensitive.
At present, the data migration task does not support tables without a non-null unique key. To avoid duplicate data in case of task restart and other exceptions, we recommend that you configure a non-null unique key for each table.
Data type mappings
| DB2 LUW database | MySQL compatible mode of OceanBase Database |
|---|---|
| TIME | TIME |
| TIMESTAMP(p) | TIMESTAMP(p), of which p indicates the number of fractional seconds. |
| DATE | DATE |
| CHAR(n) with a maximum length of 255 bytes | CHAR(n) with a length of 0 to 255 bytes |
| CHAR(n OCTETS|CODEUNITS32) Notice Only DB2 LUW 10.5 and later support the CODEUNITS32 encoding unit. |
CHAR(n) |
| CHARACTER(n) | CHAR(n) |
| CHAR(n) FOR BIT DATA | BINARY(n) |
| CHARACTER(n) FOR BIT DATA | BINARY(n) |
| VARCHAR(n) with a maximum length of 32,672 bytes | VARCHAR(n) with a length of 0 to 65,535 bytes |
| VARCHAR(n OCTETS|CODEUNITS32) Notice Only DB2 LUW 10.5 and later support the CODEUNITS32 encoding unit. |
VARCHAR(n) |
| VARCHAR(n) FOR BIT DATA | VARBINARY(n) |
| CLOB | TINYTEXT (<=255) TEXT (n<=65535) MEDIUMTEXT (n<=16777215) 16MB LONGTEXT (n<=4294967295) 2GB |
| NCLOB | TINYTEXT (<=255) TEXT (n<=65535) MEDIUMTEXT (n<=16777215) 16MB LONGTEXT (n<=4294967295) 2GB |
| GRAPHIC(n) | CHAR(n) |
| VARGRAPHIC(n) | VARCHAR(n) |
| LONG VARGRAPHIC | TINYTEXT (<=255) TEXT (n<=65535) MEDIUMTEXT (n<=16777215) 16MB LONGTEXT (n<=4294967295) 2GB |
| LONG VARCHAR | LONGTEXT |
| BINARY | BINARY |
| VARBINARY | VARBINARY |
| BLOB | TINYBLOB (<=255) BLOB (n<=65535) MEDIUMBLOB (n<=16777215) 16MB LONGBLOB (n<=4294967295) 2GB |
| BOOLEAN | BOOLEAN |
| SMALLINT | SMALLINT |
| INTEGER | INT/INTEGER |
| BIGINT | BIGINT |
| DECIMAL(p[,s]) | DECIMAL(p[,s]) |
| NUMERIC(p[,s]) | NUMERIC(p[,s]) |
| DECFLOAT(16) DECFLOAT(34) | NUMERIC(65, 30) |
| REAL | DOUBLE |
| DOUBLE | DOUBLE |
| XML | LONGTEXT(n<=4294967295) 2GB |
Procedure
Create a data migration task.
Log in to the OMS console.
In the left-side navigation pane, click Data Migration.
On the Data Migration page, click Create Task in the upper-right corner.
On the Create Task page, specify the name of the migration task.
We recommend that you set it to a combination of digits and letters. It must not contain any spaces and cannot exceed 64 characters in length.
Notice
The task name must be a unique identifier in the OMS system.
In the Select Source and Target step, configure the parameters.
Parameter Description Source If you have created a DB2 LUW data source, select it from the drop-down list. If not, click New Data Source in the drop-down list and create one in the dialog box that appears on the right. For more information, see Create a DB2 LUW data source.
Notice
The column specified as the unique key in a DB2 LUW database must have the NOT NULL constraint.Target If you have created a data source for the MySQL-compatible tenant of OceanBase Database, which can be a physical data source, a public cloud OceanBase data source, or a standalone data source, select it from the drop-down list. If not, click New Data Source in the drop-down list and create one in the dialog box that appears on the right. For more information about the parameters, see Create a physical OceanBase data source, Create a public cloud OceanBase data source, or Create a standalone OceanBase data source. Tag (Optional) Click the text box and select a tag from the drop-down list. You can also click Manage Tags to create, modify, and delete tags. For more information, see Use tags to manage data migration tasks. Click Next. In the Select Migration Type step, specify the migration types for the migration task.
Options for Migration Type are Schema Migration, Full Migration, Incremental Synchronization, and Reverse Increment.
Migration type Description Schema migration The definitions of data objects, such as tables, indexes, constraints, comments, and views, are migrated from the source database to the target database. Temporary tables are automatically filtered out. Full migration After a full migration task is started, OMS migrates existing data of tables in the source database to corresponding tables in the target database. If you select Full Migration, we recommend that you use the RUNSTATSstatement to collect the statistics of the DB2 LUW database before data migration.Incremental synchronization Changed data in the source database is synchronized to the corresponding tables in the target database after an incremental synchronization task starts. Supported data changes are data addition, modification, and deletion.
Options for Incremental Synchronization are DML synchronization and DDL synchronization. Select the options as needed. For more information, see Configure DDL/DML synchronization. Incremental Synchronization has the following limitations:- If you select DDL synchronization, when you perform a DDL operation that cannot be synchronized by OMS in the source database, data migration may be interrupted.
- If the DDL operation creates a new column, we recommend that you set the column to NULL. Otherwise, data migration may be interrupted.
Reverse increment When a reverse increment task starts, OMS migrates the data changed in the target database after the business switchover back to the source database in real time.
Generally, incremental synchronization configurations are reused for reverse increment. You can also customize the configurations for reverse increment as needed. You cannot select Reverse Increment in the following cases:- The list of migration objects contains databases or tables with lowercase names.
- Multi-table aggregation is involved.
- Multiple source schemas map to the same target schema.
(Optional) Click Next.
If you have selected Reverse Increment without configuring the related parameters for the target MySQL compatible mode of OceanBase Database, the Add Data Source Information dialog box appears, prompting you to configure related parameters. For more information about the parameters, see Create a physical OceanBase data source, Create a public cloud OceanBase data source, or Create a standalone OceanBase data source.
After you configure the parameters, click Test connectivity. After the test succeeds, click Save.
Click Next. In the Select Migration Objects step, specify the migration objects for the migration task.
You can select Specify Objects or Match by Rule to specify the migration objects. The following procedure describes how to specify migration objects by using the Specify Objects option. For information about the procedure for specifying migration objects by using the Match by Rule option, see Configure matching rules.
Notice
If a database or table name contains double dollar signs ("$$"), you cannot create the migration task.
If you have selected DDL Synchronization in the Select Migration Type step, we recommend that you select Match by Rule to specify migration objects. This way, all new objects that meet the specified rules will be synchronized. If you select Specify Objects to specify migration objects, new or renamed objects will not be synchronized.
OMS automatically filters out unsupported tables. For information about the SQL statements for querying table objects, see SQL statements for querying table objects.
In the Select Migration Objects section, select Specify Objects.
In the Source Object(s) list, select the objects to be migrated. You can select tables and views of one or more databases as the migration objects.
Click > to add the selected objects to the Target Object(s) list.
OMS also allows you to import objects by using text, rename objects, configure row filters, select columns, and remove one or all objects to be migrated.
Note
When you select Match by Rule to specify migration objects, object renaming is implemented based on the syntax of the specified matching rules. In the operation area, you can only set filter conditions. For more information, see Configure matching rules.
Operation Steps Import objects - In the Target Object(s) list, 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 Objects dialog box, import the objects to be migrated.
You can import CSV files to rename databases/tables and set row filtering conditions. For more information, see Download and import the settings of migration objects. - Click Validate.
- After the validation succeeds, click OK.
Rename objects OMS allows you to rename migration objects. For more information, see Rename a migration or synchronization object. Configure settings OMS allows you to configure row filters and specify columns to be migrated. - Hover the pointer over the target object in the right-side list of the selection area.
- Click Settings that appears.
- In the Settings dialog box, you can perform the following operations:
-
In the Row Filters section, configure row filters by entering WHERE clauses of standard SQL statements. For more information, see Use SQL conditions to filter data.
- In the Select Columns section, select the columns to be migrated. For more information, see Column filtering.
Remove one or all objects OMS allows you to remove one or all objects to be migrated to the target database during data mapping. - To remove one migration object:
In the Target Object(s) list, move the pointer over the target object and click Remove. - To remove all migration objects:
In the Target Object(s) list, click Remove All in the upper-right corner. In the dialog box that appears, click OK.
Click Next. In the Migration Options step, configure the parameters.
Schema Migration
The following parameters are displayed only if you have selected One-way Synchronization > Schema Migration in the Select Migration Type step.
Parameter Description Automatically Enter Next Stage upon Completion If you select schema migration and any other migration type, you can specify whether to automatically proceed to the next stage after schema migration is completed. The default value is Yes. You can also view and modify this value on the Schema Migration tab of the data migration task details page. Normal Index Migration Method The migration method for non-unique key indexes associated with the migrated table objects, including Do Not Migrate, Migrate with Schema, and Post-Full-Migration (displayed only when Full Migration is selected). Full migration
The following parameters are displayed only if you have selected Full Migration in the Select Migration Type step.
Parameter Description Full Migration Rate Limit You can choose whether to limit the full migration rate as needed. If you choose to limit it, you must specify the RPS and BPS. The RPS specifies the maximum rows of data migrated to the target database per second during full migration, and the BPS specifies the maximum amount of data in bytes migrated to the target database per second during full migration. Note
The RPS and BPS values specified here are only for throttling. The actual full migration performance is subject to factors such as the settings of the source and target databases and the instance specifications.
Full Migration Resource Configuration You can select Small, Medium, or Large to use the corresponding default values of Read Concurrency, Write Concurrency, and Memory. You can also customize the resource configurations for full migration. By setting the resource configuration for the Full-Import component, you can limit the resource consumption of a task in the full migration phase. Notice
In the case of custom configurations, the minimum value is
1, and only integers are supported.Handle Non-empty Tables in Target Database Valid values: Ignore and Stop Migration. - If you select Ignore, when the data to be inserted conflicts with the existing data of a target table, OMS retains the existing data and records the conflict data.
- If you select Stop Migration and a target table contains data, an error is returned during full migration, indicating that the migration is not allowed. In this case, you must clear the data in the target table before you can continue with the migration.
Notice
After an error is returned, if you click Resume in the dialog box, OMS ignores this error and continues to migrate data. Proceed with caution.
Incremental synchronization
The following parameters are displayed only if you have selected Incremental Synchronization in the Select Migration Type step.
Parameter Description Incremental Synchronization Rate Limit You can choose whether to limit the incremental synchronization rate as needed. If you choose to limit it, you must specify the RPS and BPS. The RPS specifies the maximum rows of data synchronized to the target database per second during incremental synchronization, and the BPS specifies the maximum amount of data in bytes synchronized to the target database per second during incremental synchronization. Note
The RPS and BPS values specified here are only for throttling. The actual incremental synchronization performance is subject to factors such as the settings of the source and target databases and the instance specifications.
Incremental Log Pull Resource Configuration You can select Small, Medium, or Large to use the corresponding default value of Memory. You can also customize the resource configurations for incremental log pull. By setting the resource configuration for the Store component, you can limit the resource consumption of a task in log pull in the incremental synchronization stage. Notice
In the case of custom configurations, the minimum value is
1, and only integers are supported.Incremental Data Write Resource Configuration You can select Small, Medium, or Large to use the corresponding default values of Write Concurrency and Memory. You can also customize the resource configurations for incremental data writes. By setting the resource configuration for the Incr-Sync component, you can limit the resource consumption of a task in data writes in the incremental synchronization stage. Notice
In the case of custom configurations, the minimum value is
1, and only integers are supported.Incremental Record Retention Duration The duration that incremental parsed files are cached in OMS. A longer retention duration results in more disk space occupied by the Store component. Incremental Synchronization Start Timestamp - If you have selected Full Migration as the migration type, this parameter is not displayed.
- If you have selected Incremental Synchronization but not Full Migration, specify a point in time after which the data is to be synchronized. The default value is the current system time. For more information, see Set an incremental synchronization timestamp.
Reverse increment
The following parameters are displayed only if you have selected Reverse Increment in the Select Migration Type step. The parameters for reverse increment are consistent with those for incremental synchronization. You can select Reuse Incremental Synchronization Configuration in the upper-right corner.
Advanced options
The following parameters are displayed only if the target is a MySQL-compatible tenant of OceanBase Database V4.3.0 or later and you have selected Schema Migration or DDL synchronization for Incremental Synchronization in the Select Migration Type step.
This parameter specifies the storage type for target table objects during schema migration or incremental synchronization. The storage types supported for target table objects are Default, Row Storage, Column Storage, and Hybrid Row-Column Storage. For more information, see default_table_store_format.
Note
The value Default means that other parameters are automatically set based on the parameter configurations of the target database. Table objects in schema migration and new table objects created by incremental DDL statements are written to corresponding schemas based on the specified storage type.
If the parameter settings on the page cannot meet your requirements, you can click Parameter Configuration in the lower part of the page to configure more specific settings. You can also reference an existing task or component template.
Click Precheck to start a precheck on the data migration task.
During the precheck, OMS checks the read and write privileges of the database users and the network connectivity of the databases. A data migration task can be started only after it passes all check items. If an error is returned during the precheck, you can perform the following operations:
Identify and troubleshoot the issue and then perform the precheck again.
Click Skip in the Actions column of a failed precheck item. In the dialog box that prompts the consequences of the operation, click OK.
Click Start Task. If you do not need to start the task now, click Save to go to the details page of the task. You can start the task later as needed.
You can click Configure Validation Task in the upper-right corner of the data migration details page to compare the data between the source and target databases. For more information, see Create a data validation task.
OMS allows you to modify the migration objects when the data migration task is running. For more information, see View and modify migration objects. After the data migration task is started, it is executed based on the selected migration types. For more information, see the View migration details section in View details of a data migration task.