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VMS Redundancy
C-4 VMS User Guide
Active Server Role
The active VMS server has the following specific privileges that differ from a
standby server:
• There can be only one (1) VMS server actively managing the network.
• The active server is considered the default VMS server for configuration
and network topology purposes.
• The active server's database is considered the master copy. The standby
server(s) receives a copy of the master database from the active server as a
part of its start-up process and automatic synchronization.
• The first VMS server to come on-line assumes the active mode provided
that all redundant servers are online and no other server is operating in
active mode.
• The active server is the only unit that may initiate a manual protection
switch-over (a transition from active-to-standby mode or standby-to-active
mode). This is a two-step event controlled by the operator/administrator:
the Active server is first Deactivated, then a Standby server is Activated.
Standby Server Role
A VMS standby server has the following specific functions that differ from the
active VMS server:
• Upon startup, a standby VMS enters a query-peer mode where it attempts
to discover a peer VMS in active mode. The VMS enters a standby mode
when an active VMS is discovered.
• A standby VMS server's default mode is standby. It can only enter active
as a result of a protection switch, either automatic or manual.
Automatic VMS Activation
An Auto Activate function is available to resolve any activation conflicts in the
event that all servers go offline temporarily. Once the servers return to online
status, the server that was the last active will automatically reactivate and
assume the active role.
Server Synchronization
Server synchronization is always executed by/from the active VMS server, and
is performed to ensure that all standby servers receive any necessary updates
due to changes in the master database that resides in the active server. Two
types of server synchronization occur with a redundant VMS configuration,
automatic and manual.