Installing, Upgrading, and Updating the Operating
System
The installation of software can mean a complete installation,
an upgrade, or an update. The terms have the following meanings:
Installation
Used to install a completely
new version of the operating system.
Upgrade
Used to make major changes
to an existing version of the operating system.
Update
Used to make minor changes to an existing
version of the operating system.
Refer to the following documentation for detailed instructions
on how to install and upgrade the OpenVMS operating system:
On VAX systems, refer to the most
recent versions of the OpenVMS VAX Upgrade and Installation Manual
and the upgrade and installation supplement for your VAX computer.
On Alpha systems, refer to the most recent version
of the OpenVMS Alpha Upgrade and Installation Manual.
HP OpenVMS System Manager's Manual, Volume 1:... 
Installing, Upgrading, and Updating Software