Distributed Name Service (DNS) Management Operations Manual

DNS Database Replication
How DNS Exports the Name Database
5–6 31258 Tandem Computers Incorporated
Figure 5-2. Time-Staged Replication
DNS updates name definition
on Node B.
DNS updates name definition on
Node A, but queues update
request for Node B.
User tries to update a name
definition replicated on Node B.
10:00 a.m.
Node A Node B
Node B is restored.
9:00 a.m.
Node B fails.
5
4
3
2
1
Node A Node B
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Situations might arise where a name’s definition node is unavailable and a change to
that name’s definition is required. DNS permits you to make a modifiable copy of
remotely defined names with the COPY command. Any changes made to such a copy
are strictly local and are not exported to the other systems in the name’s domain.
Once a change to a name’s definition is exported to all the systems in the name’s
domain (including those that were previously unavailable), all copies of that definition
are consistent. Changes to the definition of the existing names are processed in the
same way.