Browse Prior Art Database

Alternate Path Group ID Support

IP.com Disclosure Number: IPCOM000103440D
Original Publication Date: 1990-Nov-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 1 page(s) / 60K

Publishing Venue

IBM

Related People

Malinowski, PA: AUTHOR [+2]

Abstract

Disclosed is a method that allows a host operating system and a guest operating system to efficiently exploit the dynamic pathing feature of I/O devices. This feature enhances the performance and RAS characteristics of the devices and system.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 60% of the total text.

Alternate Path Group ID Support

      Disclosed is a method that allows a host operating system and a
guest operating system to efficiently exploit the dynamic pathing
feature of I/O devices.  This feature enhances the performance and
RAS characteristics of the devices and system.

      Upon utilization, the host operating system creates a world
wide unique path group identifier (PGID), eleven bytes in length
consisting of the following data:
           CPU serial number
           CPU model
           CPU address
           first half of time-of-day clock

      The host operating system then issues the Set-Path-Group-
Identifier channel command word to every path of every devices that
it manages.  This enables the dynamic pathing feature for all devices
and for all guest operating systems even though the guest may not
know about the dynamic pathing feature.  If a guest is given
exclusive control of a device (dedicated) the path group may have
been altered.  The host operating system always reestablishes the
path group from scratch whenever the guest operating system
relinquishes control of the device.

      When a guest operating system initializes, it also constructs a
world wide unique path group identifier in the same way that the host
operating system did.  The guest operating system then tries to
establish its own path group identifier on the device by using the
Set-Path-Group ID channel command word as d...