HFS or zFS customization volume

This is an installation-maintained volume. The data sets on this volume will not be overlaid by system replacement. This volume is separate from the HFS or zFS target volume because it may contain unshareable HFS or zFS files that will generally need to be mounted MODE(RDWR).

The recommended types of data sets for this volume are:

HFS or zFS data sets that must be in write mode (for instance, /etc, /u, /var) and contain customized information.
A user catalog to own the HFS or zFS data sets (optional). This makes the volume portable using dump and restore, catalog services (IMPORT CONNECT), and SMS definition changes.

Reasons to put these data sets on this volume are:

To keep customer HFS or zFS customization file systems separate so that they can be mounted under the file system provided in a system replace.
To improve system performance. The number of HFS or zFS data sets that must be in write mode should be minimized to just what is required.
To keep installation-maintained HFS or zFS data sets (which may be SMS-managed) together on the same volume for easier management.