DC/UCF Concepts › External User Sessions › External Request Units

External Request Units

An external request unit is an online task initiated within a DC/UCF system to service database requests from an external user session.

An external request unit is initiated when a request for database services originates from:

• A batch application
• Another DC/UCF system (using either DC-to-DC communications through an SVC or DDS)
• Another TP monitor such as CICS.
• An application executing on the PC that uses CAICCI to communicate, such as CA Visual Express

All concurrent database transactions initiated by one user session and processed on the same back-end DC/UCF system are managed as a single external request unit. All database requests issued as part of the external request unit are serviced by the same back-end task.

Specifying Runtime Characteristics of ERUs

Specify resource limits, dispatching priority and other runtime characteristics of external request units using the system generation TASK statement.

By default all external request units are serviced by a task named RHDCNP3S. The attributes defined for the RHDCNP3S task are used for all external request units processed under that task code. Alternate task codes can be defined for external request units so that different runtime characteristics are used.

Note: For more information about specifying runtime characteristics of external request units, see the CA IDMS System Operations Guide.

System Generation Requirements

The following system generation parameters are related to external request unit processing:

• Task and program definitions for RHDCNP3S
• The MAXIMUM ERUS parameter of the SYSTEM statement determines the maximum number of concurrent non-DDS external request units that can be processed by a DC/UCF system
• CHKUSER TASKS parameter of the SYSTEM statement controls a mechanism for detecting abnormally terminated batch applications in z/OS and z/VSE
• EXTERNAL WAIT parameter on the SYSTEM and TASK statements determines the amount of time the system waits between external requests before assuming that the external user session has terminated
• Additional parameters to define a DDS environment

More information:

Abend Detection and Timed Functions

DDS Sessions

External Request Elements