z/VM: CP Commands and Utilities Reference - z/VM - IBM

Restricted User IDs
in both uppercase and lowercase letters, you should not assign a user ID
that is exactly the same as any acceptable truncation of the keyword. For
example:
STORage
is a reserved keyword. You should not assign any of the following as user
IDs:
STOR
STORA
STORAG
STORAGE
1894 z/VM: CP Commands and Utilities Reference
Users should not be given user IDs that match SNA device LUNAMEs.
The formats LOGNxxxx, LOGLxxxx, and LOGVxxxx are used by the system
during the logon process. Avoid making user IDs of these forms.
Note: A one-to-four digit spoolid may be treated as a userid if it is in the directory.
The characters that you may use for user IDs specified in system configuration file
statements are restricted by the USERID_CHARACTERS and by the
USERID_PATTERN translate test tables. These tables restrict legal user ID
characters to these:
alphabetics
A through Z
numerics
0 through 9
others
@ # $ _ (underscore) - (hyphen)
It is recommended that you not use logical line editing symbols in userids. See
Appendix B, “Logical Line Editing Symbols,” on page 1895.
If you must change these legal character restrictions, please refer to the z/VM: CP
Planning and Administration.