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Resolving Alternate Paths to Facilities in Systems With Dynamic Configurability

IP.com Disclosure Number: IPCOM000038748D
Original Publication Date: 1987-Feb-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 2 page(s) / 39K

Publishing Venue

IBM

Related People

Bourke, DG: AUTHOR [+3]

Abstract

This article describes a technique for use in I/O subsystems of data processing systems which resolves alternate paths to I/O facilities, thereby eliminating ambiguity as to facilities actually shared. In a system supporting dynamic configurability where alternate paths to a given facility exist, the system configuration control program will receive multiple requests for attachment from facilities to which there are alternate paths. Since each request will have a different address for the facility, a mechanism is needed to recognize that it is exactly the same facility to preclude multiple programs connecting to the facility and to determine that alternate paths do exist to the facility in case of breakage in one of the paths.

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Resolving Alternate Paths to Facilities in Systems With Dynamic Configurability

This article describes a technique for use in I/O subsystems of data processing systems which resolves alternate paths to I/O facilities, thereby eliminating ambiguity as to facilities actually shared. In a system supporting dynamic configurability where alternate paths to a given facility exist, the system configuration control program will receive multiple requests for attachment from facilities to which there are alternate paths. Since each request will have a different address for the facility, a mechanism is needed to recognize that it is exactly the same facility to preclude multiple programs connecting to the facility and to determine that alternate paths do exist to the facility in case of breakage in one of the paths. Each program-visible facility in the system will contain a machine-readable unique serial number which, along with its type ID, will provide a unique title in the universe of facilities. This is included in the parameters passed with an attach request. The facility must originate an attach request on each port (connection) to higher level facilities if they exist. The system configuration control program, upon receipt of a new request, compares the serial number to those of the same type previously connected. If a match is found, it recognizes the address as being an alternate path and passes the new address to the attaching program as an alias address to the sa...