Another reason to limit your reliance on the webserver that InterSystems ship and install is that it will only receive security patches when you apply a maintenance update to your Cache/Ensemble/HealthShare instance. In comparison, you can (and should) take responsibility for keeping a standalone instance of webserver software (e.g. IIS, Apache) up to date with security fixes.

By setting up a gateway connection and then looking at the journal records I tracked down this global subtree:

%SYS>d ^%G
 
For help on global specifications DO HELP^%G
Global ^%SYS("sql","ODBCCONNECTION"
^%SYS("sql","ODBCCONNECTION","DATA")=1
^%SYS("sql","ODBCCONNECTION","DATA",1)=$lb("","ENS171 Samples","YJM","_system","HnBuSSuEERERntcVPGsUMQ==",0,0,"","","","",0,"",0,0,1,0,1,0,"",0)
^%SYS("sql","ODBCCONNECTION","INDEX","NameIndex"," YJM",1)=""
 
Global ^
 
%SYS>

The password (see yellow highlight) isn't stored in plaintext.