On Fri, 10 Jun 2016 16:53:42 +0530, linda golding <lindagolding...@gmail.com> wrote: >Does anyone know how OSA-ICC devices (3270-X) are mapped in HSA ? > >I did a search in our systems and see that OSA-ICC devices are concurrently >active on all LPARS of the sysplex . I also see that PCHID is same across >all the systems . I am just trying to find out how multiple systems can >write on to the same physical OSA-ICC device ?..Basically i would like to >know how this happens at hardware level . Any pointers /documentation would >be a great help .
It works because of the magic of the Multiple Image Facility, MIF. Device numbers are for the wetware. The host OS doesn't use them, but instead uses a subchannel number, for which there is a 1-1 binding with a device number in the LPAR. (The STORE SUBCHANNEL instruction provides the binding information.) For every device (UA) in the I/O config, IOCP creates a subchannel for each LPAR in the access list for the device. The metadata for the subchannel includes the owning LPAR's CSS and MIF ID. When the LPAR uses one of its subchannels to communicate with a device, the channel subsystem grabs the UA, CSS and MIF ID, and sends them with the I/O request to the CU. That means that two LPARs can use the same UA on the same CU, and the CU can tell them apart. (Yay!) Recognizing the CSS and MIF ID is what makes a device MIF-capable. Now, the extent to which a CU surfaces this knowledge to the management interfaces varies. OSA-ICC makes it very visible. You associate a TN3270E LUNAME with a particular CSS, MIF, and, optionally, a particular device number. The OSA has the distinct advantage of having access to the I/O configuration data, so it can see the device number associations and show them to you in the configuration panels, not requiring you to do the device number <-> UA translations yourself. Alan Altmark z/VM Consultant IBM Lab Services ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
