FTAM/9000 User's Guide

70 Chapter 5
FTAM File Protection
Introduction to FTAM File Protection
Introduction to FTAM File Protection
One of the key FTAM features is its sophisticated file protection scheme.
FTAM provides two related mechanisms to protect files from undesirable
or unauthorized use:
• The first—called access control —controls the actions that users
can perform on the file. A file has a list of permissions (permitted
actions), which specify the actions that are allowed to be performed
on the file (see Table 5-1). It is also possible to limit individual users
(or classes of users) to some subset of a file's permissions. For
example, one user may be allowed to read—but not modify—a certain
file, while another user can do both.
• The second—called concurrency control —controls access to a file
by multiple users (see Table 5-2). For example, a user may be allowed
to modify the file only if no one else is using it. For example, consider
the user who is not allowed to modify a file, but is allowed to read it.
To obtain a “snapshot” of the file at a given moment, the user still
needs to obtain exclusive access to the file as he reads it. Therefore, in
the command to read the file, this user must request exclusive
access—a function of concurrency control. This chapter shows to do
this.
To summarize, access control governs the actions that are permitted on
a file, granting different users different subsets of the available actions.
Concurrency control governs whether and how multiple users can
access the file. Access control and concurrency control were designed and
implemented to help ensure that data remains secure and uncorrupted.