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.
A – TRUE
The higher the power limit, the more quickly a rebalance operation can complete. Rebalancing takes longer with lower power values, but consumes fewer processing and I/O resources which are shared by other applications, such as the database.
C – TRUE
Grouping operations in a single ALTER DISKGROUP statement can reduce rebalancing operations.
http://docs.oracle.com/cd/E11882_01/server.112/e18951/asmdiskgrps.htm#OSTMG10070
E – FALSE
Otherwise, derived from the values of PARALLEL_MAX_SERVERS, PARALLEL_THREADS_PER_CPU, CLUSTER_DATABASE_INSTANCES, DISPATCHERS, and BWR_IO_SLAVES.
Note that a value derived in this way does not take into account the requirements used for Oracle Automatic Storage Management (Oracle ASM) files
On “C” they are talking about multiple operations (drop, resize, add), in out case this is a single operation. So, this is true only for multiple operations.
“You can use the ALTER DISKGROUP SQL statement to alter a disk group configuration. You can add, resize, or drop disks while the database remains online. Whenever possible, multiple operations in a single ALTER DISKGROUP statement are recommended. Grouping operations in a single ALTER DISKGROUP statement can reduce rebalancing operations.”
A and C appears to be correct.
AC
Not “D”, as according to the documentation you can have only ONE asmb process.
“ASM Background Process (ASMB)
Communicates with the ASM instance, managing storage and providing statistics
ASMB runs in ASM instances when the ASMCMD cp command runs or when the database instance first starts if the server parameter file is stored in ASM. ASMB also runs with Oracle Cluster Registry on ASM.”
http://docs.oracle.com/database/121/REFRN/bgprocesses.htm#REFRN104
Maybe they wanna say at point D, increase the number of ARB processes. And this will speed up the rebalance.
AC
Oracle ASM rebalancing operations are controlled by the size of the disks in a disk group.
Oracle ASM automatically initiates a rebalance after storage configuration changes, such as when you add, drop, or resize disks. The power setting parameter determines the speed with which rebalancing operations occur.
The ASM_POWER_LIMIT initialization parameter specifies the default power for disk rebalancing in a disk group. The range of values is 0 to 1024. The default value is 1. A value of 0 disables rebalancing. Higher numeric values enable the rebalancing operation to complete more quickly, but might result in higher I/O overhead and more rebalancing processes.
ASMB-ASM Background Process-Communicates with the ASM instance, managing storage and providing statistics-ASMB runs in ASM instances when the ASMCMD cp command runs or when the database instance first starts if the server parameter file is stored in ASM. ASMB also runs with Oracle Cluster Registry on ASM – Database and ASM instances.
ARBn-ASM Rebalance Process-Rebalances data extents within an ASM disk group-
Possible processes are ARB0-ARB9 and ARBA – ASM instance.
Choice D ias actually ARBn process and not ASMB process. It is a typo.
Answer: A, D
AC
ALTER DISKGROUP dgroup1 ADD DISK
‘/devices/diskd*’
REBALANCE POWER 5 WAIT
C
My exam said ASMB processes in one of the answers, so I chose AC.
I passed and this question didn’t show up in my feedback so I guess AC is the right answer 🙂
Anybody taken exam recently ? is the same questions or changed?
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A is clearly right
D is NOT right as ASMB process runs once (ARBn is another story as many users already said)
C is correct as you can choose rebalance power in alter diskgroup command