46 Chapter 2: Unity Architecture Overview
Unity system cares about. In short, Unity cares about any Exchange server that houses one
or more subscribers on it. These Exchange servers are added to the list of systems that the
windows manager pings every 15 seconds (in versions 3.1[3] and earlier, this was every
30 seconds). If the server is offline or the Exchange directory (in the case of Exchange 5.5)
or mail store services (for both Exchange 55 and 2000) are not responsive, or if the Service
Control Manager (SCM) itself is not responsive, this server is marked internally as being
down. When a subscriber signs into the Unity server over the phone to gain access to
messages, the conversation first checks to see whether that Exchange server is up or down
before attempting to log into that user’s mailbox. If it is down, subscribers are not allowed
to attempt the login to their mailboxes over the phone because this can result in very
long MAPI timeouts and can end with a call being stuck or “wedged” for a long period
of time. If the Exchange server that you selected during the configuration setup (the partner
Exchange server, as it is called in the documentation) is offline, Unity goes into full UMR
mode and stores voice messages locally until connectivity can be re-established.
In the case of Domino, the monitoring service cannot assume that the server is running on
top of a Windows platform, so things get a little trickier. The service simply pings the server
by name and checks for a response to make sure it is up. It does not, however, know whether
the Domino services on that server function properly.
Whenever the avWM component marks a server as being down or back up again, an event
log message is written through to the application event log. The Event Monitoring Service
(EMS) Exchange Monitor Tool introduced for Unity 4.0(2) resides in the Tools Depot. It is
designed to give the administrator the capability to be notified in a variety of ways when
specific errors or classes of errors are written to the event log. For sites that have trouble
with their external Exchange servers or that experience severe network latency issues, this
can be helpful in staying on top of such problems.
For the Unity 4.0(3) release, the notification processes that are responsible for lighting
MWIs, sending out notification e-mails, sending pages, and so on based on inbox activity
have been pulled out of the AVCsMgr group into their own process here.
What is referred to generally as “the notifier” is actually a set of three separate components.
The AVMsgStoreMonitorSvr (see the upcoming section with this name) watches all inboxes
of subscribers on the local Unity server for changes and then pushes that information onto
the notification queue. The notifier engine in the AVNotificationMgr process watches the
queue for items that it needs to react to and hands off the request to one of four device man-
agers for MWIs, SMTP (text pagers), conversations (phone notification device), or pagers

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