Emulating the S/390 read backwards tape operation on SCSI attach

Details Emulating the S/390 read backwards tape operation on SCSI attach Emulating the S/390 read backwards tape operation on SCSI attach

1998-09-24

2000-11-14

Teska, Kevin J.

Data processing: structural design, modeling, simulation, and em

Emulation

Of instruction

703 24, 703 25, 703 27, G06F 9455

Patent

active

061482781

ABSTRACT:
Disclosed is a method for attaching SCSI tape devices which may only read in a forward direction to an S/390 compatible computer system. This involves translating S/390 I/O operations for channel communication by emulating an S/390 "Read Backwards" channel command with a single "Read Backwards" routine to be used for all SCSI tape drives regardless of read capabilities in the backward direction. The emulation of a S/390 "Read Backwards" channel command includes using a combination of existing tape positioning commands, including: the RF (Read Forward) command, parsing technique to obtain the appropriate bytes to be stored into memory, and calculation for the residual byte count.

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Magstar 3590 (Magstar 3590 Tape Subsystem: Multiplatform Implementation, Chapter 3, Sections 3.1 -3.2.4, Nov. 1997 [retrieved from the Internet on Jan. 31, 2000]. Retrieved from the Internet at http://www.redbooks.ibm.com/SG242594/sg242008.htm).
Magstar 3590 Table of Contents (Magstar 3590 Tape Subsystem: Multiplatform Implementation, Table of Contents, Nov. 1997 [retrieved from the Internet on Jan. 31, 2000]. Retrieved from the Internet at http://www.redbooks.ibm.com/SG2425994/sg24254.htm.

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