Technical data

Managing Storage Media
9.1 Understanding Storage Media Concepts
9.1.4.1 Public Disk Volumes
A public volume is a file-structured disk volume that can contain both private
and public files. Public volumes can be either of the following ones:
Type of Volume Description
System volumes Available to all the users on a system
Group volumes Available to all the users in a group
As long as file protections permit it, all users have access to public volumes and
to the files on them.
One way to permit users to create and store files on a public volume is to create
a default directory on the public volume for each authorized user. You control
access to public files and volumes by the protection codes that you establish.
A user is free to create, write, and manipulate files on a public volume only under
the following conditions:
• Volume and file protection allow access, or you have privileges that allow you
to access the files.
• The user has appropriate access to a directory on the volume.
• Disk quota permits usage.
The following sections contain guidelines for setting up and maintaining public
files and volumes.
Planning Public Volumes
You must balance users’ space needs with the system’s available mass storage
resources. These determinations depend, in part, on whether you have relatively
small or large mass storage capability. A comparison of the two follows.
Configuration Characteristics
Small mass storage Both system files and user files are on the same public volume.
You might want to set disk quotas to ensure that user files do not
exhaust the free space on the disk volume.
Large mass storage Keep all system files on one disk volume (known as a system disk
or a system volume), and keep all user files on separate volumes.
The system disk is kept active reading system images, paging and
swapping, spooling files, maintaining system logs, and so forth.
The most common arrangement is to have one public volume with system files
and the directories of privileged users, and other public volumes dedicated to user
directories, databases, and applications required by your site.
Whichever arrangement you select, plan each public volume and monitor disk
performance once the system is running:
• Be sure the system disk has enough space for the operating system to boot
and accept updates.
• Once the system is running, use the Monitor utility (MONITOR) to analyze
disk use to determine whether disk I/O is balanced across the configuration.
Section 20.8 discusses this utility in detail.
You can often move system files off the system disk and use search lists or logical
names to access them. See Section 17.8 for more information.
9–14 Managing Storage Media