Task Stages |
Schema Migration and Full Data Migration are selected by default.
Note
- In this scenario, DTS does not support incremental data migration. To ensure data
consistency, we recommend that you do not write data to the source database during
data migration.
- The schema of and data in the table that is created by executing the CREATE TABLE
statement can be migrated to the destination database.
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Processing Mode of Conflicting Tables |
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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
tables that have the same names, the precheck is passed. Otherwise, an error is returned
during the 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 tables that have identical 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 ensured, 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.
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Merge Tables |
- Yes: If you select this value, DTS adds the
__dts_data_source column to each table to record data sources. For more information, see Enable the multi-table merging feature.
- No: This value is selected by default.
Note If you set this parameter to Yes, all the selected source tables in the task are merged
into a single destination table. If you do not need to merge specific source tables,
you can create a separate data migration task for these tables.
Warning We recommend that you do not perform DDL operations to change the schemas of source
databases or tables. Otherwise, data inconsistency may occur or the data migration
task fails.
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Source Objects |
Select one or more objects from the Source Objects section and click the icon to add the objects to the Selected Objects section.
Note
- You can select tables or databases as the objects to be migrated. If you select tables
as the objects to be migrated, DTS does not migrate other objects such as views, triggers,
or stored procedures to the destination database.
- If you select a database as the object to be migrated, DTS migrates data based on
the following default rules:
- If the table to be migrated in the source database has a primary key, such as a single-column
primary key or a composite primary key, the primary key columns are specified as the
distribution keys.
- If the table to be migrated in the source database does not have a primary key, an
auto-increment primary key column is automatically generated in the destination table.
This may cause data inconsistency between the source and destination databases.
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Selected Objects |
- To rename an object that you want to migrate to the destination instance, right-click
the object in the Selected Objects section. For more information, see Map the name of a single object.
- To rename multiple objects at a time, click Batch Edit in the upper-right corner of the Selected Objects section. For more information, see Map multiple object names at a time.
Note
- If you use the object name mapping feature to rename an object, other objects that
are dependent on the object may fail to be migrated.
- To specify WHERE conditions to filter data, right-click an object in the Selected Objects section. In the dialog box that appears, specify the conditions. For more information,
see Use SQL conditions to filter data.
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