Control table task settings - AWS Database Migration Service

Control table task settings

Control tables provide information about an AWS DMS task. They also provide useful statistics that you can use to plan and manage both the current migration task and future tasks. You can apply these task settings in a JSON file or by choosing Advanced Settings on the Create task page in the AWS DMS console. The Apply Exceptions table (dmslogs.awsdms_apply_exceptions) is always created.

For Full load + CDC (Migrate existing data and replicate ongoing changes) and CDC only (Replicate data changes only) tasks, you can also create additional tables, including the following:

  • Replication Status (dmslogs.awsdms_status) – This table provides details about the current task. These include task status, amount of memory consumed by the task, and the number of changes not yet applied to the target. This table also gives the position in the source database where AWS DMS is currently reading. Also, it indicates if the task is in the full load phase or change data capture (CDC).

  • Suspended Tables (dmslogs.awsdms_suspended_tables) – This table provides a list of suspended tables as well as the reason they were suspended.

  • Replication History (dmslogs.awsdms_history) – This table provides information about replication history. This information includes the number and volume of records processed during the task, latency at the end of a CDC task, and other statistics.

The Apply Exceptions table (dmslogs.awsdms_apply_exceptions) contains the following parameters.

Column Type Description

TASK_NAME

nvchar

The name of the AWS DMS task.

TABLE_OWNER

nvchar

The table owner.

TABLE_NAME

nvchar

The table name.

ERROR_TIME

timestamp

The time the exception (error) occurred.

STATEMENT

nvchar

The statement that was being run when the error occurred.

ERROR

nvchar

The error name and description.

The Replication History table (dmslogs.awsdms_history) contains the following parameters.

Column Type Description

SERVER_NAME

nvchar

The name of the machine where the replication task is running.

TASK_NAME

nvchar

The name of the AWS DMS task.

TIMESLOT_TYPE

varchar

One of the following values:

  • FULL LOAD

  • CHANGE PROCESSING (CDC)

If the task is running both full load and CDC, two history records are written to the time slot.

TIMESLOT

timestamp

The ending timestamp of the time slot.

TIMESLOT_DURATION

int

The duration of the time slot, in minutes.

TIMESLOT_LATENCY

int

The target latency at the end of the time slot, in seconds. This value only applies to CDC time slots.

RECORDS

int

The number of records processed during the time slot.

TIMESLOT_VOLUME

int

The volume of data processed in MB.

The Replication Status table (dmslogs.awsdms_status) contains the current status of the task and the target database. It has the following settings.

Column Type Description

SERVER_NAME

nvchar

The name of the machine where the replication task is running.

TASK_NAME

nvchar

The name of the AWS DMS task.

TASK_STATUS

varchar

One of the following values:

  • FULL LOAD

  • CHANGE PROCESSING (CDC)

Task status is set to FULL LOAD as long as there is at least one table in full load. After all tables have been loaded, the task status changes to CHANGE PROCESSING if CDC is enabled.

STATUS_TIME

timestamp

The timestamp of the task status.

PENDING_CHANGES

int

The number of change records that weren't applied to the target.

DISK_SWAP_SIZE

int

The amount of disk space used by old or offloaded transactions.

TASK_MEMORY

int

Current memory used, in MB.

SOURCE_CURRENT

_POSITION

varchar

The position in the source database that AWS DMS is currently reading from.

SOURCE_CURRENT

_TIMESTAMP

timestamp

The timestamp in the source database that AWS DMS is currently reading from.

SOURCE_TAIL

_POSITION

varchar

The position of the oldest start transaction that isn't committed. This value is the newest position that you can revert to without losing any changes.

SOURCE_TAIL

_TIMESTAMP

timestamp

The timestamp of the oldest start transaction that isn't committed. This value is the newest timestamp that you can revert to without losing any changes.

SOURCE_TIMESTAMP

_APPLIED

timestamp

The timestamp of the last transaction commit. In a bulk apply process, this value is the timestamp for the commit of the last transaction in the batch.

Additional control table settings include the following:

  • HistoryTimeslotInMinutes – Use this option to indicate the length of each time slot in the Replication History table. The default is 5 minutes.

  • ControlSchema – Use this option to indicate the database schema name for the control tables for the AWS DMS target. If you don't enter any information for this option, then the tables are copied to the default location in the database as listed following:

    • PostgreSQL, Public

    • Oracle, the target schema

    • Microsoft SQL Server, dbo in the target database

    • MySQL, awsdms_control

    • MariaDB, awsdms_control

    • Amazon Redshift, Public

    • DynamoDB, created as individual tables in the database