OpenVMS lets you customize the size of the operating system
by deleting or adding optional system files, including support for
DECwindows. This is particularly valuable for small systems or systems
with limited disk space.
For example, if your system is a MicroVAX II computer with
an RD54 system disk and you will not use system programming features
such as the Delta/XDelta Debugger (DELTA/XDELTA) or the System Dump
Analyzer utility (SDA), you might remove these files from the system
disk.
Depending on the system you are using, you can add or delete
files in one of the following ways:
On VAX systems, you can use the OpenVMS
Tailoring utilities, VMSTAILOR and DECW$TAILOR:
VMSTAILOR - applies to optional
system files
DECW$TAILOR - applies to support for DECwindows
Delete files from and add files to the system disk by identifying
classes and subclasses of operating system files that you want to
add or delete. You might delete or add an entire class or selected
subclasses of files within a class. If you delete files, you can add them again at any time using
VMSTAILOR or DECW$TAILOR and your operating system distribution
media. Refer to the for more information about VMSTAILOR and DECW$TAILOR.
On Alpha systems, you can use the POLYCENTER Software
Installation utility
to add or delete optional system files. Add or delete files by selecting
or deselecting options and suboptions. To invoke the POLYCENTER Software Installation utility for
this purpose, you can use either of the following methods:
Use the DCL command PRODUCT RECONFIGURE.
Use the DECwindows Motif interface from the POLYCENTER
Software Installation utility and select the Reconfigure option
on the Mode menu.
HP OpenVMS System Manager's Manual, Volume 1:... 
Customizing the Operating System
