OCP-1Z0-053-V13.02-705题

705. View Exhibit1 to examine the DATA disk group when all the disks are online.  

  

Why is the rebalancing not performed and the content of  the disk group not empty in Exhibit2?

A.Because the disk group is created with NORMAL redundancy

B.Because the disk repair time attribute is set to a nonzero value

C.Because the mirrored extents cannot be rebalanced across the other three disks

D.Because the other three disks have 60% fr ee space, the disk r ebalancing is delayed

Answer: D 

答案解析：

途中对比，发现第二文件的path没有了，题中问为什么没有重新平衡。

因为设置了DISK_REPAIR_TIME 参数，to repair the disk and bring it back online，推迟了重新平衡。

故选B。

Configuring Disk Repair Time

Specify a time period that is long enough for you to repair a disk in the disk group.

For information about disk group repair time, see "Oracle ASM Fast Mirror Resync".

http://docs.oracle.com/cd/E11882_01/server.112/e18951/asmdiskgrps.htm#OSTMG10044、

Oracle ASM Fast Mirror Resync

Restoring the redundancy of an Oracle ASM disk group after a transient disk path failure can be time consuming. This is especially true if the recovery process requires rebuilding an entire Oracle ASM failure group. Oracle ASM fast mirror resync significantly reduces the time to resynchronize a failed disk in such situations. When you replace the failed disk, Oracle ASM can quickly resynchronize the Oracle ASM disk extents.

Note:

To use this feature, the disk group compatibility attributes must be set to 11.1 or higher. For more information, refer to "Disk Group Compatibility".

Any problems that make a failure group temporarily unavailable are considered transient failures that can be recovered by the Oracle ASM fast mirror resync feature. For example, transient failures can be caused by disk path malfunctions, such as cable failures, host bus adapter failures, controller failures, or disk power supply interruptions.

Oracle ASM fast resync keeps track of pending changes to extents on an OFFLINE disk during an outage. The extents are resynced when the disk is brought back online.

By default, Oracle ASM drops a disk in 3.6 hours after it is taken offline. You can set the DISK_REPAIR_TIME disk group attribute to delay the drop operation by specifying a time interval to repair the disk and bring it back online. The time can be specified in units of minutes (m or M) or hours (h or H). If you omit the unit, then the default unit is hours. The DISK_REPAIR_TIME disk group attribute can only be set with the ALTER DISKGROUP SQL statement.

If the attribute is not set explicitly, then the default value (3.6h) applies to disks that have been set to OFFLINE mode without an explicit DROP AFTER clause. Disks taken offline due to I/O errors do not have a DROP AFTER clause.

The default DISK_REPAIR_TIME attribute value is an estimate that should be adequate for most environments. However, ensure that the attribute value is set to the amount of time that you think is necessary in your environment to fix any transient disk error, and that you are willing to tolerate reduced data redundancy.

The elapsed time (since the disk was set to OFFLINE mode) is incremented only when the disk group containing the offline disks is mounted. The REPAIR_TIMERcolumn of V$ASM_DISK shows the amount of time left (in seconds) before an offline disk is dropped. After the specified time has elapsed, Oracle ASM drops the disk. You can override this attribute with the ALTER DISKGROUP OFFLINE DISK statement and the DROP AFTER clause.