Task Stages |
Incremental Data Synchronization is selected by default. You must also select Schema Synchronization and Full Data Synchronization. After the precheck is complete, DTS synchronizes the historical data of selected
objects from the source instance to the destination cluster. The historical data is
the basis for subsequent incremental synchronization.
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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
identical table names, the precheck is passed. Otherwise, an error is returned during
the precheck and the data synchronization 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 identical table 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 inconsistency may occur and your business may be exposed to potential risks.
- If the source and destination databases have the same schema, and a data record has
the same primary key as an existing data record in the destination database:
- During full data synchronization, DTS does not synchronize the data record to the
destination database. The existing data record in the destination database is retained.
- During incremental data synchronization, DTS synchronizes the data record to the destination
database. The existing data record in the destination database is overwritten.
- If the source and destination databases have different schemas, initial data synchronization
may fail. In this case, only part of the columns are synchronized, or the data synchronization
task fails.
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DDL and DML Operations to Be Synchronized |
Select the DDL and DML operations that you want to synchronize. For more information,
see SQL operations that can be synchronized.
Note To select the SQL operations performed on a specific database or table, perform the
following steps: In the Selected Objects section, right-click an object. In the dialog box that appears, select the SQL operations
that you want to synchronize.
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Merge Tables |
- Yes: In online transaction processing (OLTP) scenarios, sharding is implemented to speed
up the response to business tables. In online analytical processing (OLAP) scenarios,
you can store a large amount of data in a single table. It makes your SQL queries
more efficient. This way, you can merge multiple source tables that have an identical
schema into a single destination table. This feature allows you to synchronize data
from multiple tables in the source database to a single table in the destination database.
Note
- After you select multiple tables from the source database, you must change the names
of these tables to the name of the destination table by using the object name mapping
feature. For more information about how to use this feature, see Map object names.
- DTS adds a column named
__dts_data_source to the destination table. This column is used to record the data source. The data
type of this column is TEXT. The values of this column are in the following format:
data synchronization instance ID:source database name:source schema name:source table
name . This allows DTS to identify each source table. Example: dts********:dtstestdata:testschema:customer1 .
- If you set this parameter to Yes, all the selected source tables in the task are merged
into a destination table. If you want to merge only part of the source tables, you
must create a separate data synchronization 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 migration task
fails.
- No: the default value.
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Select 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 columns, tables, or databases as objects to synchronize. If you select
tables or columns as the objects to synchronize, DTS does not synchronize other objects
such as views, triggers, and stored procedures to the destination database.
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Rename Databases and Tables |
- To rename an object in 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 in the destination instance, click Batch Edit in the upper-right corner of the Selected Objects section. For more information, see Map multiple object names at a time.
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Filter data |
You can specify WHERE conditions to filter data. For more information, see Use SQL conditions to filter data.
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Select the SQL operations to be synchronized |
In the Selected Objects section, right-click an object. In the dialog box that appears, select the SQL operations
that you want to synchronize. For more information, see SQL operations that can be synchronized.
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