Browse Prior Art Database

Inhibiting Input Output Retries

IP.com Disclosure Number: IPCOM000052793D
Original Publication Date: 1981-Jul-01
Included in the Prior Art Database: 2005-Feb-11
Document File: 2 page(s) / 46K

Publishing Venue

IBM

Related People

Robinson, FL: AUTHOR [+2]

Abstract

The present disclosure is an improvement over the channel command retry (CCR) set forth in U. S. Patent 3,688,274. In a control unit having plural levels of control, a channel level can provide channel command retries to received commands. A more remote level of control, such as a microprocessor or device adapter, can inhibit the sending of a CCR by the channel level whenever an error condition has occurred, an anomaly status has been generated or because of other unique status. In particular, when a subsystem is attempting to respond to the subsequently reissued command (following the end of the full CCR sequence), then the subsystem's ability to inhibit further CCR on that command is beneficial.

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Inhibiting Input Output Retries

The present disclosure is an improvement over the channel command retry (CCR) set forth in U. S. Patent 3,688,274. In a control unit having plural levels of control, a channel level can provide channel command retries to received commands. A more remote level of control, such as a microprocessor or device adapter, can inhibit the sending of a CCR by the channel level whenever an error condition has occurred, an anomaly status has been generated or because of other unique status. In particular, when a subsystem is attempting to respond to the subsequently reissued command (following the end of the full CCR sequence), then the subsystem's ability to inhibit further CCR on that command is beneficial.

A plurality of hosts each have a plurality of channels which are connected to a plurality of devices via plural channel adapters and device adapters which in turn are controlled by a plurality of programmed controls. I/O commands are sent from the channel to the channel adapter. The channel adapter decodes the command as a first level of control. The programmed control constitutes a second level of control and coordinates operation of the channel adapters and device adapters. Because of conditions in the subsystem, such as a device not being ready, a data path not having been established, and the like, a command can be rejected by the channel adapter with a CCR being sent to the channel. The programmed control, device adapter, devices and...