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Self-Configuring Tape Driver for Emulated and Non-Emulated Tapemarks

IP.com Disclosure Number: IPCOM000117563D
Original Publication Date: 1996-Mar-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 2 page(s) / 76K

Publishing Venue

IBM

Related People

Bhaskaran, DR: AUTHOR [+3]

Abstract

A method of automatically configuring a tape device driver for handling the overwrite characteristics of a tape device is described.

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

Self-Configuring Tape Driver for Emulated and Non-Emulated Tapemarks

      A method of automatically configuring a tape device driver for
handling the overwrite characteristics of a tape device is described.

      In a self-configuring tape device driver or application, it is
necessary to determine certain characteristics dynamically so that
the device can be properly run by the driver.  One important
characteristic concerns the ability to over-write data on the tape
media.  Devices have  been designed with the following overwrite
characteristics:
  a) Some devices are not able to over-write data or tapemarks, but
      can only append to the tape at the end of data, or overwrite
the
      entire tape from the beginning.
  b) Some devices are able to only over-write tapemarks (or special
      tapemarks), the entire tape from the beginning, or at the end
of
      data (blank tape).
  c) Some devices are able to over-write data at any position.

      In order to support the later type of devices for appending on
standard-labeled tapes, it is necessary to perform a standard-labeled
tape emulation.  To do this, the driver will not write the second
tapemark at the end of a file.  Then later, when reading the tape,
the tapemark is emulated when blank tape is encountered.  When that
emulated tapemark needs to be overwritten, there is no tapemark to
actually overwrite, and a new file can be appended to the tape
successfully.

      It is not possible to perform this same emulation on the
devices which support overwriting anywhere since blank tape does not
work reliably for these types of devices, thus it is absolutely
necessary to determine which type of device is present to determine
how many tapemarks to write at the end of a file so that subsequent
files can be appended properly on standard-labeled tapes.

      In order to write a generic driver which could run any type of
tape device, the following algorithm was implemented.  The following
terminology is used in the following description:
  a) Type...