Browse Prior Art Database

Design for File Transfer with the Host Processor

IP.com Disclosure Number: IPCOM000118339D
Original Publication Date: 1996-Dec-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 4 page(s) / 116K

Publishing Venue

IBM

Related People

Gallagher, RJ: AUTHOR [+5]

Abstract

Files of any defined size may be passed over a 200 Mb ESCON link between host processor systems and the fixed disk of a PS/2* attached via a slow bus to an ESCON control unit without wasting link bandwidth.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 51% of the total text.

Design for File Transfer with the Host Processor

      Files of any defined size may be passed over a 200 Mb ESCON
link between host processor systems and the fixed disk of a PS/2*
attached via a slow bus to an ESCON control unit without wasting link
bandwidth.

      In the Figure, an ESCON Director (14) is shown containing ports
(16) connecting to a switching matrix (3), a control unit element (1)
connecting to an internal link (2), and a IEEE 488 interface (4)
connecting the control unit element (1) to a console (5) (a PS/2).
For a typical file (approximately 6KB) about 25 ms are required to
access the file on the fixed disk (6), 50 ms are required to pass the
file across the 488 interface (4) and 3 ms are required to pass the
file over the ESCON link (7) to the host processor (8).  Since the
host processor serial channel (9) to which the switched ESCON link

(7) attaches is shared with other control units (15), it should not
be tied up for any longer than the 3 ms required to pass the file
over the ESCON link (7).

      To achieve this objective, block buffers (10,11) were
implemented in the control unit (1) and a file buffer (12) was
implemented in the local console (5).  Since some of the file types
which might be transferred were about 58KB and since available RAM in
the control unit (1) was very limited, the implementation allows the
block buffers (10,11) to be significantly smaller than the complete
file.  Functions were defined as follows:
  1.  Query - This function allowed host programming to determine
       the names of files already saved on the fixed disk (6) and
       determine the number of block buffers (10,11) contained in
       the complete file.
  2.  File Locking - This function allowed the file being accessed
       to be locked.  This is required because the shared
       environment used for controlling the ESCON Director allows
       access from multiple host systems (8,13) and the local
       console (5).  File locking is required to precede each
       of the functions described below.
  3.  Read File - This function is used to read a file or portion
       of a file.  The function is preceded by use of the File
       Locking function and is implemented using a combination
       of two commands, Identify and Read Block.  Following the
       Read File function the Release function is used to conclude
       the operation.

          To perform the function, the Identify command is used to
    specify the file and the number of the block to be read.  Status
    containing channel end only is presented while the file is read
    from the fixed disk (6) into the file buffer (12) and the block
    specified is read from the file buffer (12) into the block buffer
    (10).  If multiple block buffers (11) have been implemented,
    additional sequential blocks are read into the block...