PMDF System Manager's Guide
26.5.2 The Order in Which Entries are Checked
The logic for checking entries in the profile database (UNIX only), 
pipe database and pipe channel option file is as follows:
  -  (UNIX only) Check the profile database for a  
user@host
 entry.
   -  Check the database for a  
user@host
 entry.
   -  Check the option file for a   
user@host
 entry.
   -  Check the database for a  
host
 entry.
   -  Check the option file for a   
host
 entry.
 
If no profile database entry exists (as is always the case on OpenVMS) 
and if the pipe database does not exist, then only the pipe option file 
is checked, i.e., steps (3) and (5) only. If no profile 
database entry exists (as is always the case on OpenVMS) and if the 
database file exists but cannot be opened, then the message is passed 
over --- the condition is treated as a temporary error. And when checks 
(1)--(5) turn up no results, the message is bounced.