Design overview

The purpose of the NEP is to allow user-dependent processing whenever a communication system event is reported to CICS®. An example of the processing that can be done is to analyze the event and override the default action set by DFHZNAC. When NEP processing is complete, control returns to DFHZNAC.

The default node error program sets the ‘print TCTTE’ action flag (TWAOTCTE in the user option byte TWAOPT1, defined in DFHNEPCA) if a VTAM® storage problem has been detected; otherwise, it performs no processing, and leaves the action flags set by DFHZNAC unchanged.

The skeleton sample NEP provided by CICS can provide extended error handling for VTAM terminals, and is generated by means of the DFHSNEP macro. This procedure is described in the CICS Customization Guide.

The DFHSNEP macro can also be used to generate a user-written NEP. Interactions between the applications and VTAM depend on characteristics of the transactions and the installation. Each system has different characteristics. The CICS-provided skeleton NEP is a framework for a user-written NEP to handle network error conditions that may be unique to a particular installation.

Guidance information about NEP coding is given in the CICS Recovery and Restart Guide. Reference information about NEP coding is given in the CICS Customization Guide.

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