The Question is:
Where do i find the information concerning the system-logical
The Answer is :
Start with the OpenVMS Master Index manual, looking up MAIL$SYSTEM_FLAGS.
You will there find that MAIL$SYSTEM_FLAGS is documented in the OpenVMS
System Manager's Manual (V7.2 edition) Section 5.7 "Customizing Mail".
(In the hardcopy document set, this particular manual is called the
"OpenVMS System Manager's Manual: Essentials".)
Here is an extract. (Please see the documentation for full details.)
The value of the logical name MAIL$SYSTEM_FLAGS is interpreted in the
1 Indicates that this node is part of a homogeneous OpenVMS1 Cluster
system. In other words, all disks are accessible to the cluster, and
a common SYSUAF file and a common mail file exist for the cluster.
When this bit is set, the system checks the node to which you are
sending mail to see if it is currently in the cluster. If the node is
in the cluster, the system bypasses DECnet, and the message is written
directly to the recipient's mail file. (Note that the node must be up
to determine whether it is part of the cluster.)
2 Directs Mail to set the OpenVMS Cluster system breakthrough flag when
issuing the $BRKTHRU service to notify the recipient of new mail. This
flag is used only in OpenVMS Cluster systems and, typically, only in
homogeneous OpenVMS Cluster systems (in other words, flag 1 is also
4 Directs Mail to include the time the message was delivered in the
notification message displayed on the recipient's terminal.
8 Directs Mail to use DECnet VAX address syntax when the system is
running DECnet-Plus. (VAX specific)
16 Directs Mail to use DECnet-Plus address syntax. (VAX specific)