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Use of Command Retry Function to Free Channel Interface

IP.com Disclosure Number: IPCOM000076062D
Original Publication Date: 1972-Jan-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Schor, MI: AUTHOR

Abstract

A special use of a function for retrying a command in a storage control unit can be implemented to result in freeing the channel interface, so that it is able to service other control units while the subsystem is performing some relatively long operation which does not need channel communication. Two cases of this are while the control unit is padding to index and chaining, and while the control unit is moving the access mechanism prior to operating on a command requiring reading or writing on the file. In these situations, the command must first be received to determine that the cases exist;, i.e., for padding, any command other than a format write must be received, and for the access movement, a read, write, or search command must be received with the specific type of operation required.

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Use of Command Retry Function to Free Channel Interface

A special use of a function for retrying a command in a storage control unit can be implemented to result in freeing the channel interface, so that it is able to service other control units while the subsystem is performing some relatively long operation which does not need channel communication. Two cases of this are while the control unit is padding to index and chaining, and while the control unit is moving the access mechanism prior to operating on a command requiring reading or writing on the file. In these situations, the command must first be received to determine that the cases exist;, i.e., for padding, any command other than a format write must be received, and for the access movement, a read, write, or search command must be received with the specific type of operation required.

After the command is received and the case isolated, a signal is sent to the channel to retry the command, the signal being accomplished with channel end status only, to disconnect from a channel operating in block multiplex mode. When the subsystem operation is complete, the storage control unit reconnects using the Request-In function and presents device end status. The channel then reissues the command and continues normally.

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