With IPHost Network Monitor you can run simple snmp requests against a IBM device in your network.
ibmappnMemorySize
IBM APPN Memory Size
1.3.6.1.4.1.2.6.2.13.1.7.1
Size of the shared memory chunk, as obtained by memory management from the underlying operating system, that is allocated to this APPN node.
Back to ibm-mem MIB page.
IPHost Network monitor allows you to monitor ibmappnMemorySize on IBM device via the SNMP protocol. Download IPHost Network Monitor (500 monitors for 30 days, 50 monitors free forever) to start monitoring IBM computers right now.