The DGRP1 diskgroup has these attributes:
Normal redundancy
Two failgroups with four asmdisks in each failgroup
compatible.asm set to 12.1
The ASM_POWER_LIMIT is currently set to 1 in the ASM instances.
There are three databases whose instances are up and which access data in the DGRP1 diskgroup.
No other clients use this diskgroup.
You want to add two asmdisks to each failgroup, complete the rebalance as quickly as possible, by avoiding checks for access to allocation units, and then restore
database availability.
Examine the list of actions (see exhibit):
Exhibit:
Identify the correct sequence of required steps:
A.
1, 2, 3, 4, 5, 2, 10, 7
B.
1, 3, 5, 7
C.
1, 8, 6, 3, 5, 8, 9, 7
D.
1, 8, 6, 3, 5, 2, 10, 7
Explanation:
C
Rebalance operations that occur while a disk group is in RESTRICTED mode eliminate the lock and unlock extent map messaging that occurs between Oracle ASM instances in an Oracle RAC environment. This improves the overall rebalance throughput. At the end of a maintenance period, you must explicitly dismount the disk group and remount it in normal mode.
C
In restricted mode, database instances cannot use the disk groups. In other words, databases cannot open files that are in that disk group. Also, the disk group cannot be mounted by any other instance in the cluster. Mounting the disk group in restricted mode enables only one Oracle ASM instance to mount the disk group. This mode is useful to mount the disk group for repairing configuration issues.
About Restricted Mode
You can use the STARTUP RESTRICT command to control access to an Oracle ASM instance while you perform maintenance. When an Oracle ASM instance is active in this mode, all of the disk groups that are defined in the ASM_DISKGROUPS parameter are mounted in RESTRICTED mode. This prevents databases from connecting to the Oracle ASM instance. In addition, the restricted clause of the ALTER SYSTEM statement is disabled for the Oracle ASM instance. The ALTER DISKGROUP diskgroup MOUNT statement is extended to enable Oracle ASM to mount a disk group in restricted mode.
When you mount a disk group in RESTRICTED mode, the disk group can only be
mounted by one instance. Clients of Oracle ASM on that node cannot access that disk group while the disk group is mounted in RESTRICTED mode. The RESTRICTED mode enables you to perform maintenance tasks on a disk group in the Oracle ASM instance without interference from clients.
Rebalance operations that occur while a disk group is in RESTRICTED mode eliminate the lock and unlock extent map messaging that occurs between Oracle ASM instances in an Oracle RAC environment. This improves the overall rebalance throughput. At the end of a maintenance period, you must explicitly dismount the disk group and remount it in normal mode.
mount
Purpose
Mounts a disk group.
Syntax and Description
mount [–restrict] { [-a] | [-f] diskgroup[ diskgroup …] }
Table 55 lists the syntax options for the mount command.
Table 55 Options for the mount command
Option Description
diskgroup Name of the disk group.
-a Mounts all disk groups.
–restrict Mounts in restricted mode.
-f Forces the mount operation.
…
Why to dismount disk group to add disks? Can be done online.
B.
If You’ve already shudtown those databases. Why do you need to mount diskgroup in Restrict mode just to add more disks.
I think “B” is the correct answer.
Correct is C:
From D81242GC11 – ASM Administration:
“The rebalance operation that occur while a disk group is in restricted mode eliminate the lock and unlock extent map messaging that occurs between the SM instances in a clustered environment. This improves the overall rebalance throughput. At the end of the maintenance period, you must explicitly dismount the dis group and remount it in normal mode”