640 TCP/IP stacks (1920 devices) support – OSA-Express2, OSA-Express3, OSA-Express4S, and OSA-Express5S

When specific software levels are met (see 640 TCP/IP stacks), it is possible to specify more than 160 TCP/IP stacks per QDIO OSD OSA-Express2 and OSD and OSX OSA-Express3 CHPID and newer (OSA-Express does not support more than 160 stacks). This support disables OSA priority queuing and provides 1920 unit addresses for device number assignment. The support is enabled (turned "on") through the CHPID definition in HCD or IODF.

A good use of this support is for more than 160 Linux TCP/IP stacks in one z/VM LPAR. Up to 640 Linux stacks can be defined (1920 subchannels divided by 3 devices/subchannels per Linux TCP/IP stack). Note that to define all 1920 devices in one LPAR, multiple control units will have to be used.

For more information, refer to 640 TCP/IP stacks.

HCD notes relating to 160 and 640 TCP/IP stacks:

• After completing the Add Channel Path HCD panel, if you are running z/OS V1.6 or newer and the server is z990 or later, and the channel type is OSD or OSX, the Allow for more than 160 TCP/IP stacks panel is displayed, asking if more than 160 TCP/IP stacks will be defined: Yes or No. This window will not appear if the channel type is OSE or OSN.
• If No is specified, 480 subchannel addresses will be generated for the CHPID, and priority queuing will be supported on this CHPID. If you are coding an IODF flat file, code parameter CHPARM=00 on the CHPID macro, or do not code it at all; CHPARM=00 is the default.
• If Yes is specified, 1920 subchannel addresses will be generated for the CHPID, and priority queuing will not be supported on this CHPID. If you are coding an IODF flat file, code parameter CHPARM=02 on the CHPID macro.
  Note: A Yes reply is valid only on QDIO OSD OSA-Express2 and QDIO OSD, OSM, and OSX OSA-Express3 and newer CHPIDs. If Yes is specified for an OSD OSA-Express CHPID, a definition error will appear on the CHPID icon on the SE/HMC after the IODF is loaded.