On Wed, 8 Jun 2016 20:27:21 +0530, linda golding <[email protected]> wrote:
>Thanks Curt ... For shared DASD devices , UCW is same in HSA which is used >to serialize when IO requests from multiple LPARS arrives to the same >device . > >I was expecting something similar for console devices . But it appears that >that is not the case for consoles . I hope the hardware gurus in this List >can clarify . > > >Linda > When IOCP generates a basic IOCDS, it creates one subchannel for each I/O device associated with a logical control unit. When IOCP generates an LPAR IOCDS, the number of subchannels it generates for the group of I/O devices associated with a logical control unit depends on the number of logical control units generated for the group of I/O devices. The total number of subchannels it generates for the group of I/O devices is the number of I/O devices in the group multiplied by the number of logical control units generated for that group. The device may be a physically identifiable unit, or it may be housed internal to a control unit. In all cases a device, from the point of view of the channel subsystem, is an entity that is uniquely associated with one subchannel and that responds to selection by the channel subsystem by using the communication protocols defined for the type of channel path by which it is accessible.Then, the subchannel number is another way for addressing an I/O device. It is a value that is assigned to the subchannel (UCW) representing the device at POR time. It indicates the relative position of the UCW in the UCW table. The subchannel number was designed to speed up the search of a UCW during SSCH processing. Robert Hahne ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
