OCP-1Z0-053-V12.02-74题

74.Immediately after adding a new disk to or removing an existing disk from an ASM instance, you find
that the performance of the database goes down initially until the time the addition or removal process is
completed, and then gradually becomes normal.
Which two activities would you perform to maintain a consistent performance of the database while
adding or removing disks? (Choose two.)
A. Define the POWER option while adding or removing the disks.
B. Increase the number of ARB processes by setting up a higher value for ASM_POWER_LIMIT.
C. Increase the number of DBWR processes by setting up a higher value for
DB_WRITER_PROCESSES.
D. Increase the number of slave database writer processes by setting up a higher value for
DBWR_IO_SL***ES.
Answer: AB

答案解析：
参考：http://docs.oracle.com/cd/E11882_01/server.112/e18951/asmdiskgrps.htm#OSTMG94118

Manually Rebalancing Disk Groups

You can manually rebalance the files in a disk group using the

REBALANCE

clause
of the

ALTER DISKGROUP

statement. This would normally not be required, because Oracle
ASM automatically rebalances disk groups when their configuration changes. You might want to do a manual rebalance operation to control the speed of what would otherwise be an automatic rebalance operation.
The

POWER

clause of the

ALTER

DISKGROUP

...

REBALANCE

statement specifies the degree of parallelism, and thus the speed of the rebalance operation. It can be set to a minimum
value of 0 which halts a rebalancing operation until the statement is either implicitly or explicitly re-run. A higher value increases the speed of the rebalance operation.

Example 4-9 Manually rebalancing a disk group
ALTER DISKGROUP data2 REBALANCE POWER 5 WAIT;
The default rebalance power is set by the

ASM_POWER_LIMIT

initialization parameter. The range of values for the

POWER

clause is the same for the

ASM_POWER_LIMIT

initialization parameter.