Browse Prior Art Database

Local Sector Generation

IP.com Disclosure Number: IPCOM000050191D
Original Publication Date: 1982-Sep-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 2 page(s) / 34K

Publishing Venue

IBM

Related People

Christian, JH: AUTHOR [+5]

Abstract

A cached peripheral storage system has a DASD (direct-access storage device) backing store which is addressable by device, track, and rotational position or sector. Host communications are via a virtual system involving device address DADDR, track, and record number. To access the DASD, the peripheral storage system converts the record number to a sector number and then transfers data between the cache and the DASD. Accessing the record in the cache is by record number.

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 64% of the total text.

Page 1 of 2

Local Sector Generation

A cached peripheral storage system has a DASD (direct-access storage device) backing store which is addressable by device, track, and rotational position or sector. Host communications are via a virtual system involving device address DADDR, track, and record number. To access the DASD, the peripheral storage system converts the record number to a sector number and then transfers data between the cache and the DASD. Accessing the record in the cache is by record number.

A host makes a data access request to a cache. A directory indicates whether or not the requested data, identified by DADDR, track and record, is in cache. If the record is not in cache, then it is transferred automatically from DASD to cache and then to the requesting host. For transferring data from cache to DASD, the same procedure is followed.

From the directory, the DADDR, track ADDR, and record numbers are supplied to a control. Included in the control is a translator which takes the record numbers and generates the appropriate sector values for each of the received record numbers. The DADDR, track ADDR, and sector values are then supplied to access circuits which then access the DASD for transferring data to cache or for receiving data from cache.

The generated sector values allow for minimum latency time since no channel turnaround time is involved. For fixed length records, the translator is a table lookup. The record number is summed modulo the number of records p...