Browse Prior Art Database

Recovery From Contingent Connection Errors

IP.com Disclosure Number: IPCOM000053193D
Original Publication Date: 1981-Sep-01
Included in the Prior Art Database: 2005-Feb-12
Document File: 2 page(s) / 31K

Publishing Venue

IBM

Related People

Iskiyan, JL: AUTHOR [+4]

Abstract

Peripheral subsystems when reporting error conditions maintain a contingent connection to the host receiving the error condition indication such that sense data relating to the contingent connection can be sent to the host. In a multiple-unit peripheral subsystem, a host may be owed a contingent connection; if the host fails, then the multiple unit peripheral subsystem may have to be restarted from scratch because the subsystem cannot itself remove the contingent connection. The present article relates to using a time out in a control unit for timing a contingent connection such that an internal system reset can be generated in the subsystem for allowing hosts other than the failing host to proceed with data processing operations.

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Recovery From Contingent Connection Errors

Peripheral subsystems when reporting error conditions maintain a contingent connection to the host receiving the error condition indication such that sense data relating to the contingent connection can be sent to the host. In a multiple- unit peripheral subsystem, a host may be owed a contingent connection; if the host fails, then the multiple unit peripheral subsystem may have to be restarted from scratch because the subsystem cannot itself remove the contingent connection. The present article relates to using a time out in a control unit for timing a contingent connection such that an internal system reset can be generated in the subsystem for allowing hosts other than the failing host to proceed with data processing operations.

The figure shows a plurality of hosts A and B connected to a plural unit peripheral subsystem having three control units CU-0 through CU-2, a subsystem controller and a plurality of devices which are connectable to any of the hosts via any of the control units. The dash line indicates a contingent connection is owed by CU-0 to host B. This contingent connection is established in the control unit check (error condition). The contingent connection will be maintained by CU-0 until a command is received from a host other than TEST I/O or NO OP or a selective or system reset occurs. During the contingent connection state, the control unit CU-0 is busy to all addresses other than the address for whi...