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Here at Bobcares, we handle similar requests from our customers as a part of our AWS Support Services.

Today let’s see how our Support Engineers help our customers to create a task in AWS DMS and enable control tables.

AWS DMS tasks and control tables

AWS Database Migration Service helps to migrate databases to AWS securely. An AWS DMS task is where all the work happens. We have to specify the source, target, and replication instance, along with the migration settings.

Before creating a task, always make sure to create a source endpoint, a target endpoint, and a replication instance. The Control tables provide information about the AWS DMS task. They are used only for change data capture (CDC) operations.

Create a task in AWS DMS and enable control tables

Now let’s see the steps followed by our Support Tech to create an AWS DMS task and enable control tables.

Creating a task in AWS DMS

1. Log in to the AWS Management Console and open the AWS DMS console.

2. Then select Database migration tasks.

3. Select Create task.

4. On the Create Task page, specify the task options like source, and target endpoints and the Replication instance.

5. Then select any one of the following migration methods for Migration type:

Migrate existing data
Migrate existing data and replicate ongoing changes
Replicate data changes only

6. Then click on the Task Settings tab, and specify values for the target table, Include LOB columns in replication, and to enable logging.

7. For the target table, select any of the following:

Do nothing – In this mode, DMS assumes that the tables have been created already on the target. If a table doesn’t exist, DMS creates the table.
Drop tables on target – In this mode, AWS DMS drops the tables on the target and recreates them.
Truncate – In this mode, the DMS truncates all tables on target before the migration.

8. For Include LOB columns in replication, select any of the following:

Don’t include LOB columns – This mode excludes all LOB columns from migration.
Full LOB mode – This mode migrates all LOBs regardless of size. We can specify the LOB chunk size. AWS DMS fetches LOBs in chunks controlled by the Max LOB size parameter.
Limited LOB mode – In this mode, we can specify the maximum LOB size and truncate LOBs to the value of the Max LOB size parameter. This mode is faster than the Full LOB mode.

9. Then select enable logging, note that by enabling logging, the task requires additional time to complete.

10. Then click on the Table mappings tab, here we can set values for schema and the mapping method.

Enable control tables

1. Click on the Advanced task settings.

2. Then, In the Create control table in target using schema field, enter a schema for the control table.

The tables will copy to the default location in the database if we didn’t enter anything in the schema field. The following are the default locations for each database engine:

MySQL, MariaDB- awsdms_control
SQL Server – dbo in target database
PostgreSQL,Amazon Redshift – Public
Oracle – the target schema
Amazon Redshift – Public

3. HistoryTimeslotInMinutes –  This option is to indicate the number of minutes that each record remains in the Replication history table.

4. Then enable the following for the control tables:

Apply exceptions – This table can’t be disabled. It contains the exceptions, errors, and information of  running the process
Replication status – This table gives details about the present task, which includes task status, memory consumption, etc.
Suspended tables – This table lists the suspended tables and the reason for the suspension.
Replication history – This table gives information about replication history.

5. Then select Create task.

6. Finally, run the task, and check the target database for the schema and tables.

To change the control table settings

If we want to change the control table settings for the task,

1. Select Database migration tasks.
2. Choose the task,
3. Choose Actions.
4. Then choose Modify.
5. From the Advanced task settings tab, we can change the Control table settings.
6. After finish, Save it.

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Conclusion

To conclude, today we saw how our Support Techs help our customers to create a task in AWS DMS and enable control tables.