FTAM/9000 Programmer's Guide

Chapter 1 33
HP FTAM/9000 Overview
Overview of FTAM Concepts
FTAM Shadow Files
Because the VFS is generalized, certain VFS concepts have no direct
correspondence to the HP-UX file system. For example, a VFS file might
have fixed-length records. Such records are not defined for the HP-UX
file system.
To provide HP-UX files with FTAM VFS attributes, HP-UX uses two
files: an actual file and an optional shadow file.
• The actual file contains the data for the file. The ownership and
permissions for the file are related to, but distinct from, the FTAM
attributes for the file.
• The shadow file contains only the FTAM VFS attributes for the file.
The actual and shadow files taken together make an “FTAM file.” The
shadow file for an HP-UX file has the same name as the HP-UX file,
prefixed by “._”. For example, the FTAM file named myfile has a
corresponding shadow file named ._myfile. Like all files that begin with a
period, FTAM shadow files can be listed with the following command:
$ ls -a
Certain FTAM attributes—such as document type—exist only in the
shadow file. Other FTAM attributes—such as file name—are mapped to
normal HP-UX file attributes. Some FTAM attributes—such as access
control— include a combination of HP-UX file attributes and shadow file
information.
The shadow file is not always necessary to read or delete a file. For these
actions, FTAM uses default attributes. However, whenever FTAM
creates or modifies a file, it always creates a corresponding shadow file.
NOTE Other FTAM products from other vendors may implement the VFS using
methods other than shadow files.
Shadow File Cautions. Use caution when employing HP-UX
utilities with FTAM-related files. The following examples illustrate the
kinds of issues that can arise:
• If you use mv to rename or relocate an FTAM-related file, the
corresponding shadow file will not be rename or relocated.
Subsequent FTAM access to the file will use default VFS attributes,
which may or may not apply.