Delete Task Option | Teradata Parallel Transporter - Delete Task Option - Parallel Transporter

Teradata® Parallel Transporter Reference

Parallel Transporter
Release Number
February 2022
English (United States)
Last Update
Product Category
Teradata Tools and Utilities

The Delete Task option is unique to the Update operator. It deletes rows more quickly than using a single DELETE SQL statement.

When the DeleteTask attribute is set to 'Y', rows are deleted from a single table based on values other than a unique primary index (UPI) equality condition. A Delete Task option uses a single session and a single instance.

The Delete Task option is a good choice when a large percentage of rows in a table need to be deleted, such as deleting all rows with a transaction date prior to a specified date.

The Delete Task option operates very similarly to the standard DELETE statement in the Update operator, with the following differences:

  • Deleting based on non-index columns is normal for the Delete Task option.
  • Deleting based on a primary index, although possible, has certain limitations:
    • An equality test of a UPI value is not permitted.
    • An inequality test of a UPI value is permitted.
    • An equality test of a NUPI value is permitted.
  • A single DELETE statement is used in the APPLY statement.
  • The Delete Task option does not include an acquisition phase because there are no varying input records to apply.
  • The application phase reads each target block and deletes qualifying rows.
  • Altered blocks are written back to disk.

When the Delete Task option is specified, the Update operator functions as a standalone operator, that is, not as the usual consumer operator that reads from a source data stream. The exception is when the Delete Task is invoked by an APPLY statement that includes a WHERE clause, and the source data stream contains only a single row. In this case, the Update operator with the Delete Task option still functions as a consumer operator.

The following rules apply to a Delete Task operation regardless of whether it functions as a standalone or consumer operator:

  • Only one session is connected.
  • Only one instance is specified.
  • Only one DML group is specified.
  • Only one DML statement in the DML group is specified.
  • Only a single DELETE statement is used.
  • Only one target table is specified.
  • The first error table is not used and is ignored.
  • Only one data record is provided if using a WHERE clause.