OCP-1Z0-053-V12.02-115題

115.What are the advantages of variable extent size support for large ASM files? (Choose two.)

A. It improves resync operations when the disk comes online after being taken offline for maintenance purposes.

B. It improves performance in the extended cluster configuration by reading from a local copy of an extent.

C. Fewer extent pointers are needed to describe the file and less memory is required to manage the extent maps in the shared pool.

D. This feature enables faster file opens because of the reduction in the amount of memory that is required to store file extents.

Answer: CD

答案解析：

參考：http://docs.oracle.com/cd/E11882_01/server.112/e18951/asmcon.htm#OSTMG94064

C.隻需要較少的區指針就可以描述檔案以及隻需要較少的記憶體去管理在共享池中的區映像。

D.此功能可以更快地打開檔案，因為需要存儲檔案區的記憶體量減少。

Extents

The

contents of Oracle ASM files are stored in a disk group as a set, or collection, of extents that are stored

on individual disks within disk groups. Each extent resides on an individual disk. Extents consist of one or more allocation units (AU). To accommodate increasingly larger files, Oracle ASM uses variable size extents.

Variable size extents enable support for larger Oracle ASM data files, reduce SGA memory requirements for very large databases, and improve

performance for file create and open operations. The initial extent size equals the disk group allocation unit size and it increases by a factor of 4 or 16 at predefined thresholds. This feature is automatic for newly created

and resized data files when specific disk group compatibility attributes are set to 11.1 or higher. 

The extent size of a file varies as follows: