Avocent DSView Installer/User Manual page 103

During replication, the spoke server sends all of its database changes since the last replication to the
hub server. The hub server then incorporates those changes and sends all of its database changes
since the last replication to the spoke server (excluding the changes that spoke server just sent to the
hub server).
If an item is added on a spoke server, and another item with the same name (but perhaps with
different configuration parameters) is added on the hub server, then after replication, both items
will appear on both the hub and spoke servers, with a tilde (~) and a number added to one of the
names. The administrator should handle the issue appropriately - in some cases, the duplicate item
may need to be renamed; in others, the duplicate item should be deleted.
When different changes are made to one existing item, two outcomes are possible. For example,
assume an item is added and configured on the hub server and is then replicated to the spoke server.
Later, an administrator changes something about the item on the spoke server. Another
administrator then changes something about the item on the hub server. When the replication task
runs, two things may happen.
In a few instances where no conflict occurs, both changes will be incorporated and replicated. For
example, if the hub server's administrator adds username JaneDoe to the existing user-defined user
group Accounting and the spoke server's administrator adds username JohnDoe to the Accounting
user group, both names will be added and replicated.
In most other instances where the changes are mutually exclusive or some other conflict occurs, the
most recent change will be the only change accepted and replicated. For example, if the hub
server's administrator associates a unit with the Miami site, and the spoke server's administrator
associates the same unit with the Chicago site, the change that was made closest to the time of
replication (that is, the most recent change) will be accepted and replicated.
This emphasizes the importance of ensuring the hub and spoke servers' clocks are synchronized.
The exception to the last-change rule is when one of the actions deletes an item - in that case, the
deletion is accepted and replicated, regardless of timing. For example, if a unit was deleted on the
hub server, and then the contact information for the same unit was changed on the spoke server a
minute later, the unit will be deleted when the replication task is run.
On a spoke server, you may enable a replication task property that forces the spoke server to
retrieve a snapshot of the hub database rather than synchronizing changes back and forth. The
snapshot is a copy of the hub at the time of the operation. This feature is not normally used; it is
intended to help recover a system when replication has failed.
To display replication results and/or change the replication schedule for a spoke
server:
1. On the spoke server, click the System tab.
2. Click Tasks in the top navigation bar. The Tasks window will open.
3. Select the Database Replication task. The Task Results - Database Replication window will
open. This window contains the results of the most recent replication.
4. To display or change the replication schedule, click Schedule in the side navigation bar. The
Task Schedule - Database Replication window will open.
Chapter 3: DSView 3 Software Servers 83