Browse Prior Art Database

Bus Quiescence for Tape Minimization

IP.com Disclosure Number: IPCOM000099305D
Original Publication Date: 1990-Jan-01
Included in the Prior Art Database: 2005-Mar-14
Document File: 2 page(s) / 86K

Publishing Venue

IBM

Related People

Glantz, WH: AUTHOR [+4]

Abstract

Described is a technique which improves of an I/O processor (IOP) by suspending non-tape on a device function controller interface (DFCI) during tape reinstruct for system I/O architecture writes.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Bus Quiescence for Tape Minimization

       Described is a technique which improves of an I/O
processor (IOP) by suspending non-tape on a device function
controller interface (DFCI) during tape reinstruct for system I/O
architecture writes.

      An IOP manages requests to both tape and non-tape access
storage devices (DASDs), diskette) devices to the same DFCI bus.
These devices are being in parallel and thereby contend for and use
IOP

      To address this problem, the technique comprises the features:
 All requests except the tape operation are dynamically
 suspended at the start of tape reinstruct.
 No new non-tape requests are initiated until tape
 reinstruct has finished
 Any interrupts posted for suspended devices are deferred
 until tape reinstruct has completed.
 A fail-safe mechanism insures that tape errors do not
 cause a dead lock of suspended requests or interrupts.

      In order for tape to operate in streaming mode during writes,
the IOP needs to insure that the tape has data the tape head is in
the correct physical position. tape devices insert a gap between each
logical request enable the IOP to reinstruct the tape device.  The
IOP begin sending the tape device data before the tape has passed the
gap; otherwise, the tape must reposition when it receives the new
data, a backhitch.  The time repositioning the tape significantly
lowers the tape and ties up the IOP resources already allocated the
tape request.

      The IOP implements the DFCI architecture and, between tape
requests, polls for and receives a response sends a new tape command,
receives a data ready and then initiates the next data transfer. this
period (known as the reinstruct time), the...