We started putting PAV aliases into SS1 to save on UCBs. It does make for an interesting IODF. The only issue was with z/VM. We have several z/VM lpars along with our z/OS lpars. z/VM currently can't handle PAV aliases in SS1, they have to be in SS0.
Thanks.. Paul Feller AGT Mainframe Technical Support -----Original Message----- From: IBM Mainframe Discussion List [mailto:[email protected]] On Behalf Of John Eells Sent: Friday, January 05, 2018 05:53 To: [email protected] Subject: Re: Accessing 65536 devices Jesse 1 Robinson wrote: > We would like to be able to access >65535 device addresses (UCBs) from a > single LPAR via a single IODF. The need is for bringing a new DASD subsystem > online while retaining the old subsystem until all volumes can be copied > across. We currently have spare UCBs available, but not enough to have all > old and new devices online at the same time. Is this possible? You can have a maximum of 65,280* devices (not quite 64K) in Subchannel Set 0. There are some things that can be accessed via other SCSs, but IIRC the exceptions don't allow you to have more than 65,280 primary devices online concurrently. That includes all devices, of course, including networking, tape, consoles, and such. If replication and PAVs are eating into SCS0, you can move the secondaries to another SCS to "make room" in SCS0 for additional primary devices. When last I looked, these could be defined in other SCSs: - PPRC secondary devices - PAV aliases - FlashCopy target devices Perhaps that would free up enough slots in SCS0 for you. (It seems to work for almost everyone.) There is a very narrow exception to the above for IPLing from nonzero subchannel sets for a small number of volumes. (I don't have that list handy, but IIRC it includes at least the IPL and IODF volumes but not many more than that.) * We reserve 256 subchannels in SCS0 for future use. -- John Eells IBM Poughkeepsie [email protected] ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
