This document describes the functionality of Natural in CICS Multi-Region (MRO) Environments.
It covers the following topics:
When the NTCICSP parameter COMARET is set to ON, Natural session
data are kept in two different CICS regions:
The session restart information is kept in the COMMAREA linked to the terminal entry in the CICS terminal owning region (TOR).
The actual session data are kept in the CICS application owning region (AOR); that is, the thread or roll facility.
This may lead to inconsistencies when, for example, the AOR is restarted, but the TOR still contains old "pending" Natural sessions; resuming such a session results in a corresponding error message.
When COMARET
is set to OFF, all Natural session data are kept in the AOR, thus preventing
the inconsistencies mentioned above.
However, there may be a security concern when a terminal is removed from the TOR (either back to VTAM or by switching the session manager or power off), and another terminal dialing to this TOR receives the ID of the removed terminal and enters the Natural transaction code: then this terminal resumes the session of the previously removed terminal because of the restart information in the AOR's temporary storage, which contains the terminal ID as part of the queue name.
To prevent such a situation, a node error program (NEP) can be installed (see Node Error Program and Timeout Considerations for Natural and Natural CICS Sample Programs), which terminates a Natural session when the associated terminal is removed.