070-342 questions
Microsoft Exchange Server 2013 070-342 : Advanced Solutions of Microsoft Exchange Server 2013

070-342 Latest Exam Braindumps

Question 13: You have a database availability group (DAG). The DAG is configured as shown in the
following table.
You need to prevent a split-brain condition if a restore operation of the DAG occurs.
What should you do?
A. Deploy an alternate witness server to each site.
B. Modify the Datacenter Activation Coordination (DAC) mode.
C. Set the quorum model of the cluster to Node and Disk Majority.
D. Deploy another Mailbox server to Site2.
Correct Answer: B
Explanation:
Datacenter Activation Coordination (DAC) mode is a property setting for a database availability group
(DAG). DAC mode is disabled by default and should be enabled for all DAGs with two or more
members that use continuous replication.
If a catastrophic failure occurs that affects the DAG (for example, a complete failure of one of the
datacenters), DAC mode is used to control the startup database mount behavior of a DAG. When DAC
mode isn't enabled and a failure occurs that affects multiple servers in the DAG, and then when a
majority of the DAG members are restored after the failure, the DAG will restart and attempt to
mount databases. In a multi-datacenter configuration, this behavior could cause split brain
syndrome, a condition that occurs when all networks fail, and DAG members can't receive heartbeat
signals from each other. Split brain syndrome can also occur when network connectivity is severed
between datacenters. Split brain syndrome is prevented by always requiring a majority of the DAG
members (and in the case of DAGs with an even number of members, the DAG's witness server) to be
available and interacting for the DAG to be operational. When a majority of the members are
communicating, the DAG is said to have quorum.