Increasing host subarea element addresses

For APPN resources, VTAM® maintains a table of network addresses used only by VTAM. To increase the number of APPN sessions VTAM can support, VTAM allows extended host element addressing using the ENHADDR=YES start option. If ENHADDR=YES is specified, high-order addresses are assigned for the primary LU (and often the secondary LU as well) when the addresses of both the primary LU and secondary LU are assigned by the same VTAM (not by an NCP). This includes only sessions where both session partners are either a VTAM application or an LU that is attached to VTAM (not to an NCP). The maximum number of extended address elements that can be assigned is 33 161 216. To monitor the number of extended addresses currently in use at any time, use the D NET,STATS,TYPE=VTAM command. Stat 165 displays such a count in decimal format.

To further extend the usage of enhanced host element addressing, high-order element addresses are assigned for EE PUs, EE lines, RTP PUs, and DLUR-served PUs (when possible). This is done regardless of the coding of the ENHADDR start option.

Note: The extended and base address in use counts (stats 164 and 165 from the D NET,STATS,TYPE=VTAM command) might be one greater than the respective highwater values (stats 161 and 162 from the D NET,STATS,TYPE=VTAM command). This is because the addresses specified by the highwater values are actual addresses from a pool beginning with value 0, while the address counts are actual counts of addresses in use from that pool of addresses.