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Browse Prior Art Database

Method to Manage the Mapping of Logical to Physical Record

IP.com Disclosure Number: IPCOM000117035D
Original Publication Date: 1995-Dec-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 2 page(s) / 58K

Publishing Venue

IBM

Related People

Chiang, RK: AUTHOR [+3]

Abstract

DFSMS/MVS Network File System Server enables remote workstation user's transparent access to data stored in MVS. It provides file sharing between MVS and other remote workstations connected in a TCP/IP network through NFS protocols. Improving performance of file accessing procedures in heterogeneous network is a vital objective of DFSMS/MVSNFSS.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 55% of the total text.

Method to Manage the Mapping of Logical to Physical Record

      DFSMS/MVS Network File System Server enables remote workstation
user's transparent access to data stored in MVS.  It provides file
sharing between MVS and other remote workstations connected in a
TCP/IP network through NFS protocols.  Improving performance of file
accessing procedures in heterogeneous network is a vital objective of
DFSMS/MVSNFSS.

      The native MVS file system is record-oriented where data are
organized in logical records; as opposed to a byte-oriented file
system in a workstation where data are a single byte stream.  For
data access protocols such as NFS_READ and NFS_WRITE procedures, the
requested data are specified with a byte stream offset and size.
DFSMS/MVS NFSS must first convert the byte stream offset to the
appropriate logical record, and then map the logical record number to
a physical location in disk before data can be accessed.  The
overhead in mapping a byte stream offset to a physical location can
significantly affect the data access performance of DFSMS/MVS NFSS.

      Disclosed is a method to manage the mapping of a logical record
to a physical disk location with a double linked list of blocks that
is far more efficient than a singly linked list.  A block is an array
which contains contiguous entries with mapping information of a
logical record to the physical location (TTR) of the data block on
DASD.  The block is doubly linked for ease of searching.

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