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The sample node error program
The sample node error program provides a general environment for the execution
of error processing routines (error processors), each of which is specific to certain
error codes generated by the node abnormal condition program. Sufficient optional
error processors for normal operation of VTAM 3270 or interactive logical unit
networks are provided; these can be easily supplemented or replaced by
user-supplied error processors.
There are three types of error that may occur in a VTAM network:
v Errors in the host system
v Communication errors, such as session failures
v Abnormal conditions at the terminal, such as intervention required and invalid
requests.
A sample node error program is supplied with CICS, and can be used as the basis
of each subsequent node error program that you write. This provides you with:
v A general environment within which your error processing programs can be
added
v The default node error program in a system that has several node error
programs.
The CICS-supplied sample node error program is described in greater detail below.
Compatibility with the sample terminal error program
Receipt of sense or status codes corresponds to error codes X'D9', X'DC', X'DD',
and X'F2'. Weighted counts of these messages are maintained against numeric and
time thresholds. If the numeric threshold is exceeded, default actions are taken. If
the time threshold is reached, the count is reset. This is equivalent to the function in
the sample TEP, except that sense or status arising out of the “from” device on a
COPY command is now presented to the node error program as an error on the “to”
device; this causes the threshold to be exceeded, resulting in the request being
terminated, although the terminal remains in service. Some of the weights for errors
that occur on the 3270 display device have been revised, but otherwise the weight
and threshold values are the same as the defaults used in the sample TEP. Time
threshold maintenance for the sample NEP is mandatory, and not optional as in the
sample TEP.
For further information about time and threshold count limits, see the information
about the sample terminal error program in Chapter 8, “Writing a terminal error
program,” on page 449.
The 3270 message ‘unavailable printer’ corresponds to error code X'42' (interval
control PUT request has failed). The algorithm used for printer selection differs in
VTAM support. The retry algorithm in the sample node error program is similar to
this new selection algorithm.
Components of the sample node error program
The sample node error program comprises the following components:
v An entry section.
v The routing mechanism.
v The node error table.
v Optional common subroutines.
496 Customization Guide