Rockwell Automation 1757-SWKIT3200 ProcessLogix R320.0 Installation and Upgrade Guide - Manual (Page 222)

Publication 1757-IN032B-EN-P - April 2001
6-6 New Functions and Features
Engineering Tools Network Diagnostic Manager
The Network Diagnostic Manager (NDM) has been modified to run on
both the primary and the backup server. On the primary server, NDM
does everything that it did previously. On the backup server, NDM now
monitors the health of RSLinx and the PCIC (without generating
notifications). Furthermore, NDM has been modified to detect various
critical communication failures and stop the CDA Server service to
allow for redundant server failover. Prior to stopping the CDA Server
service, an indication of the specific communication fault detected is
both appended to the Error Log and posted as a diagnostic alarm
when running on the Primary, but only appended to the Error Log
when running on the Backup. NDM interprets the following conditions
as critical communication failures:
•
PCIC device reports major fault status. NDM immediately begins
processing to stop the CDA Server service.
•
Lost communication with PCIC device. NDM requires a fixed
number of consecutive occurrences (4) before commencing
processing to stop the CDA Server service.
•
Unable to communicate to PCIC device through configured
RSLinx driver. NDM requires a fixed number of consecutive
occurrences (5) before commencing processing to stop the CDA
Server service.
•
Lost communication with RSLinx. After NDM verifies that the
RSLinx process is not running, NDM immediately begins
processing to stop the CDA Server service.
TIP
NDM does not have the facilities to determine
whether or not it is running in a primary
synchronized server. As a consequence, the above
behavior applies equally to a non-redundant server,
the primary server (synchronized or not) and the
backup server (synchronized or not).
The rational being that at least this consistent
behavior results in user notification of the problem.
The occurrence of one the failures listed above on a
Redundant Process Server Primary will trigger a
Server failover if the Servers were synchronized and
configured for a failover on the detection of a hybrid
communications failure.