Browse Prior Art Database

Buffering by Logical Record Instead of Physical Sector

IP.com Disclosure Number: IPCOM000102838D
Original Publication Date: 1990-Feb-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 2 page(s) / 90K

Publishing Venue

IBM

Related People

Bakke, BE: AUTHOR [+4]

Abstract

The disclosed technique implements routines in a machine's Licensed Internal Code to allow effective buffering for an I/O device while hiding characteristics of the device from an operating system. The operating system handles I/O requests based upon a user record length.

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

Buffering by Logical Record Instead of Physical Sector

      The disclosed technique implements routines in a machine's
Licensed Internal Code to allow effective buffering for an I/O device
while hiding characteristics of the device from an operating system.
The operating system handles I/O requests based upon a user record
length.

      The technique involves several steps.  First, when the Licensed
Internal Code within the machine receives a request for data, the
request is divided into 3 parts.  The first part is any data between
the starting location in the file and the next physical or logical
sector boundary.  The second part is any integer multiple of the
sector size.  The final part is any data remaining after the last
complete sector.  An overview of this division is provided in Fig. 1.

      With this data division completed, the actual I/O to the device
is set up to accomplish the request.  The actual I/O to the device
consists of 1 request which involves transferring data from all of
the sectors even partially involved in the original request.  This is
required because only complete blocks can be transferred to or from
the device.  A picture showing the data to be transferred is shown in
Fig. 2.

      The device independence of the operating system code above the
machine interface is achieved by carefully describing the locations
where the data is placed as it comes from the device.  First, the
initial physical sector is read into storage.  However, these data
are not placed directly in the specified buffer.  Instead, the data
transfer is set up so that the data not requested by the operating
system are pl...