Browse Prior Art Database

New Channel Command Word Command

IP.com Disclosure Number: IPCOM000085332D
Original Publication Date: 1976-Mar-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 2 page(s) / 28K

Publishing Venue

IBM

Related People

Yates, LW: AUTHOR

Abstract

A new channel command word (CCW) command 10 is proposed which allows the reading of a full track of stored information of unknown format on one disk revolution.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 100% of the total text.

Page 1 of 2

New Channel Command Word Command

A new channel command word (CCW) command 10 is proposed which allows the reading of a full track of stored information of unknown format on one disk revolution.

The command code 11 causes the reading of the entire track of information 12 into contiguous storage in core including the count, key and data portions. The command further adds a control byte 13 to the information as it is transferred to core, the byte being appended to the last record of the track to indicate whether it is a track overflow segment or not, i.e., whether the last record had been written with the Write Special command code.

The CCW 10 has the standard CCW format and the data address 14 is a pointer to the core address containing the track data 12 and byte 13. The CCW may be used by allocating a full track length buffer and reading the track into core. Thus, the residual count from the channel status word (CSW) would be available for determining the total data length and the location of the overflow indicator 13. The overflow indicator is used when the information is being restored to the file, to determine whether the last record must be written with a Write Special command.

Alternatively, strings of the CCW's could be used to read many tracks into core. The track buffers could be scanned in core to locate the indicator byte 13 for the individual tracks.

1

Page 2 of 2

2

[This page contains 2 pictures or other non-text objects]