Browse Prior Art Database

Hierarchical Directories On CMS Minidisks

IP.com Disclosure Number: IPCOM000119870D
Original Publication Date: 1991-Mar-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 5 page(s) / 182K

Publishing Venue

IBM

Related People

Bozman, BP: AUTHOR [+3]

Abstract

A hierarchical file organization improves CMS file management and organization. It can also reduce the need for multiple minidisks. This disclosure describes how to support hierarchical directories on CMS minidisks while maintaining compatibility with the current CMS file system structure and existing CMS programs.

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Hierarchical Directories On CMS Minidisks

      A hierarchical file organization improves CMS file
management and organization. It can also reduce the need for multiple
minidisks. This disclosure describes how to support hierarchical
directories on CMS minidisks while maintaining compatibility with the
current CMS file system structure and existing CMS programs.

      The flat CMS file system makes file organization very
difficult.  In order to organize files into meaningful parts, the CMS
user must use multiple minidisks. But, minidisk management is even
more complicated since minidisks are fixed in size and users can only
access up to 26 minidisks at any one time. Finally, because the CMS
limits file names and types to eight characters, it is difficult to
group files with meaningful names.

      This article describes a technique which extends the CMS file
system to support a hierarchical organization. There are three major
parts:
1.   The structure on external storage (the minidisk) is basically
unchanged. Traditionally, the directory for a CMS minidisk is a
standard fixed-format, CMS file which only the CMS file system
manipulates. The user is not aware of its existence. With
hierarchical directories, a minidisk can contain many directory files
that are still managed only by new or modified CMS file system code.
Now, the user can see these directory files and manipulate them. "The
Real Directory Tree", described later, is a sample hierarchical
directory on a minidisk. Directory management is very simple. For
most functions, such as erase and rename, directory files are treated
the same as any other CMS file.

      2.   The structure in CMS virtual storage ("The Virtual
Directory Tree" and "The Virtual Storage Structure" being described
later) has an expanded control block structure, called Shadow ADTs,
which add a second dimension to the file directory structure. The
Shadow ADT concept is key to this disclosure.
      The Active Device Table (ADT) is a CMS control block which
defines each accessed minidisk. Each ADT is assigned a mode letter
from "A" to "Z" by the user, which limits CMS to 26 active minidisks
at any one time. Shadow ADTs allow an unlimited number of ADTs to be
associated with each mode letter and to represent an unlimited number
of directories from the same minidisk. The new structure still has an
ADT which represents both the minidisk and the root directory as
accessed by mode letter. From the root ADT, there is now a chain of
Shadow ADTs -- one for each additional directory.
      The relation and structure among different CMS mode letters is
still the same. The new structure only affects the organization
within a mode letter (a minidisk). During a search for a file on a
minidisk, CMS traverses the Shadow ADT chain in the order defined by
the Path function.

      3.   Using the new control block structure in storage as a
base, a set of new functions and techniques help CMS manag...