z/OS V1R7.0 Communications Server SNA provides messages to alert the operator when the ISTGENERIC or ISTMNPS coupling facility structures are near or have reached a structure full condition. z/OS V1R7.0 Communications Server SNA issues the following unsolicited messages when these structures are nearing a structure full condition:
IST1439I percent PERCENT OF storage_type USED FOR STRUCTURE
IST1725E STORAGE SHORTAGE IN structure_name - UNABLE TO
See the z/OS V1R7.0 Communications Server SNA Messages book for details on these messages.
If you are running z/OS V1R7.0 Communications Server with a program operation application (POA) that is not authorized as a primary program operator (AUTH=PPO is not coded on the APPL statement), VTAM will issue these unsolicited messages via WTO, using descriptor code 11. Descriptor code 11 identifies the message as a critical eventual action required message.
If, however, you are running with a POA that is authorized as a PPO (AUTH=PPO is coded on the APPL statement), VTAM does not issue a WTO for unsolicited messages. Instead, the message information is passed to the PPO application using the program operator interface (POI). Note that by design the POI interface does not pass the descriptor code for unsolicited messages to the PPO program. This means that critical messages, like IST1439I and IST1725E are not highlighted.
For example, we code AUTH=PPO on the APPL statment to use TME/10 Netview as a PPO. By default in our environment, the IST1439I and IST1725E messages are eventually written to our consoles, but are not flagged as critical eventual action messages (because descriptor code 11 is not passed to the PPO program). As a result, early warnings of structure storage shortages were easily missed by our operators and we have experienced disruptions when structures later became full.
If you are running z/OS V1R7.0 Communications Server with a POA authorized as a PPO, we recommend that you customize your automation product to make sure it recognizes the IST1439I and IST1725E messages and alerts the appropriate operators to the structure shortage condition.