Coding for session failures

Following some categories of error associated with logical unit or path failures, the session between CICS® and the logical unit may be lost. The default action taken by DFHZNAC may be to put the TCTTE out of service.

About this task

A method of automatically reacquiring the session is for your node error program to alter the default DFHZNAC actions and to keep the TCTTE in service. Your node error program can then issue an EXEC CICS START TERMID(name) command against that TCTTE for a transaction written in a similar manner to the CICS “good morning” signon message (CSGM). When the transaction is initiated using automatic transaction initiation (ATI), CICS tries to reacquire the session. If the session fails again, DFHZNAC is reinvoked and the process is repeated.

The time specified on the EXEC CICS START command is determined by installation-dependent expected-mean-time-to values.

If used in this way, the initiated transaction can write an appropriate signon message when the session has been acquired. Note, however, that if LOGONMSG=YES is specified on the CEDA DEFINE TYPETERM command, the CICS “good morning” message is also initiated when the session is opened. Refer to Restrictions on the use of EXEC CICS commands.