You administer an online transaction processing (OLTP) system whose database is stored in
Automatic Storage Management (ASM) and whose disk group use normal redundancy.
One of the ASM disks goes offline, and is then dropped because it was not brought online before
DISK_REPAIR_TIME elapsed.
When the disk is replaced and added back to the disk group, the ensuing rebalance operation is
too slow.
Which two recommendations should you make to speed up the rebalance operation if this type of
failure happens again?
A.
Increase the value of the ASM_POWER_LIMIT parameter.
B.
Set the DISK_REPAIR_TIME disk attribute to a lower value.
C.
Specify the statement that adds the disk back to the disk group.
D.
Increase the number of ASMB processes.
E.
Increase the number of DBWR_IO_SLAVES in the ASM instance.
Explanation:
A: ASM_POWER_LIMIT specifies the maximum power on an Automatic Storage
Management instance for disk rebalancing. The higher the limit, the faster rebalancing will
complete. Lower values will take longer, but consume fewer processing and I/O resources.
D:
* Normally a separate process is fired up to do that rebalance. This will take a certain amount of
time. If you want it to happen faster, fire up more processes. You tell ASM it can add more
processes by increasing the rebalance power.
* ASMB
ASM Background Process
Communicates with the ASM instance, managing storage and providing statistics
Incorrect:
Not B: A higher, not a lower, value of DISK_REPAIR_TIME would be helpful here.
Not E: If you implement database writer I/O slaves by setting the DBWR_IO_SLAVES parameter,
you configure a single (master) DBWR process that has slave processes that are subservient to it.
In addition, I/O slaves can be used to “simulate” asynchronous I/O on platforms that do notsupport asynchronous I/O or implement it inefficiently. Database I/O slaves provide non-blocking,
asynchronous requests to simulate asynchronous I/O.
Should be A and D
may be A and C
The given answer, AD, is wrong. A is correct. The ASM_POWER_LIMIT can be set to any value from 0 to 11. 0 meaning re-balancing operations are disabled, 1 meaning re-balancing operations would be the slowest and 11 meaning re-balancing operations would be the fastest. So, there are 11 settings were re-balancing is enabled. This maps to the ASM background processes which actually perform the re-balancing. They are called ARBn, where n ranges from 0 to 9 and A (A is hexadecimal for 10). Hence, you could have 11 ARB processes running ARB0 through ARB9 plus ARBA. If answer D had referenced ARBn processes instead of ASMB, then it would be correct. However, the ASMB process only comes into effect when the ASMCMD cp command runs or when an database instance first starts up and its SPFILE is stored in ASM. ASMB is also involved with OCR (Oracle Cluster Registry). So, it has nothing to do with re-balance operations. Correct answer, just A or AD if D referred to ARBn not ASMB.
H*T*H
A,D is correct.
A is obviously true, because ASM_POWER_LIMIT is:
“ASM_POWER_LIMIT specifies the maximum power on an Automatic Storage Management instance for disk rebalancing. The higher the limit, the faster rebalancing will complete. Lower values will take longer, but consume fewer processing and I/O resources.
If the POWER clause of a rebalance operation is not specified, then the default power will be the value of ASM_POWER_LIMIT.”
https://docs.oracle.com/cd/B28359_01/server.111/b28320/initparams012.htm#REFRN10246
D is also true, but they’re being tricky here. To “Increase the number of ASMB processes” you have to alter the ASM_POWER_LIMIT. In fact that’s what changing the ASM_POWER_LIMIT does, it increases the number of ASMB processes.
See:page 757 http://www.amazon.com/Oracle-Database-All-Guide-CD-ROM/dp/0071629181
A and C is the best, D is also correct but…
“C” cannot be correct because question already states “… When the disk is replaced and ADDED back to the disk group …”. So the disk is already added to the disk-group. Hence why would you “C. Specify the statement that adds the disk back to the disk group.” if disk is already added.
I would rather go with “D” (and of course A).
A is obvious
second should be C becauase ALTER DISKGROUP command support a POWER parameter
D is not correct from the reason stated by H*T*H
A & C
AD