You must configure an Oracle Data Guard environment consisting of:
1. A primary database
2. A Physical Standby Database
3. A Snapshot Standby Database
You must meet these requirements:
1. Primary database availability should not be compromised by the availability of the standby databases.
2. Under normal operations, transactions executed on the primary database should not commit before redo is
written to disk on the primary database and on at least one standby database.
Which redo transport mode, and which protection mode should you configure to meet these requirements?
A.
SYNC AFFIRM and Maximum Protection
B.
SYNC NOAFFIRM and Maximum Protection
C.
SYNC AFFIRM and Maximum Availability
D.
SYNC NOAFFIRM and Maximum Availability
E.
ASYNC and Maximum Performance
Explanation:
The Maximum Availability protection mode provides the highest level of data protection that is possible without
compromising the availability of a primary database. Transactions do not commit until all redo data needed to
recover those transactions has been written to the online redo log and to at least one synchronized standby
database. If the primary database cannot write its redo stream to at least one synchronized standby database,
it operates as if it were in maximum performance mode to preserve primary database availability until it is again
able to write its redo stream to a synchronized standby database.
This mode ensures that no data loss will occur if the primary database fails, but only if a second fault does not
prevent a complete set of redo data from being sent from the primary database to at least one standby
database.When a transport is performed using SYNC/AFFIRM, the primary performs write operations and waits for
acknowledgment that the redo has been transmitted synchronously to the physical standby and written to disk.
A SYNC/AFFIRM transport provides an additional protection benefit at the expense of a performance impact
caused by the time required to complete the I/O to the standby redo log.
Incorrect Answers:
D: In the case of SYNC/NOAFFIRM, in which there is no check that data has been written to disk on the
standby, there may be some data loss.
A, B: The Maximum Protection mode ensures that zero data loss occurs if a primary database fails. To provide
this level of protection, the redo data needed to recover a transaction must be written to both the online redo
log and to at least one synchronized standby database before the transaction commits. To ensure that data
loss cannot occur, the primary database will shut down, rather than continue processing transactions, if it
cannot write its redo stream to at least one synchronized standby database.
Because this data protection mode prioritizes data protection over primary database availability, Oracle
recommends that a minimum of two standby databases be used to protect a primary database that runs in
maximum protection mode to prevent a single standby database failure from causing the primary database to
shut down.
E: The Maximum Performance protection mode provides the highest level of data protection that is possible
without affecting the performance of a primary database. This is accomplished by allowing transactions to
commit as soon as all redo data generated by those transactions has been written to the online log. Redo data
is also written to one or more standby databases, but this is done asynchronously with respect to transaction
commitment, so primary database performance is unaffected by delays in writing redo data to the standby
database(s).
This protection mode offers slightly less data protection than maximum availability mode and has minimal
impact on primary database performance.
This is the default protection mode.
https://docs.oracle.com/cd/B28359_01/server.111/b28294/protection.htm
C
C