Which two statements are true about variable extent size support for large ASM files?
A.
The metadata used to track extents in SGA is reduced.
B.
Rebalance operations are completed faster than with a fixed extent size
C.
An ASM Instance automatically allocates an appropriate extent size.
D.
Resync operations are completed faster when a disk comes online after being taken offline.
E.
Performance improves in a stretch cluster configuration by reading from a local copy of an
extent.
Explanation:
A: Variable size extents enable support for larger ASM datafiles, reduce SGA
memory requirements for very large databases (A), and improve performance for file create and
open operations.
C: You don’t have to worry about the sizes; the ASM instance automatically allocates theappropriate extent size.
Note:
* The contents of ASM files are stored in a disk group as a set, or collection, of data 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,
ASM uses variable size extents.
* The size of the extent map that defines a file can be smaller by a factor of 8 and 64 depending
on the file size. The initial extent size is equal to the allocation unit size and it increases by a factor
of 8 and 64 at predefined thresholds. This feature is automatic for newly created and resized
datafiles when the disk group compatibility attributes are set to Oracle Release 11 or higher.
AC
AC
A-C
ASM does not eliminate any existing database f
unctionality. Existing databases are able to
operate as they always have. New files may be
created as ASM files, whereas existing ones
are administered in the old way or can be migrated to ASM.
The diagram illustrates the relationships betw
een an Oracle database data file and the ASM
storage components. The crow’s foot notation represents a one-to-many relationship. An
Oracle Database data file has a one-to-one rela
tionship with either a file stored on the
operating system in a file system or an ASM file.
An Oracle ASM disk group is a collection of one or more Oracle ASM disks managed as a
logical unit. The data structures in a disk group ar
e self-contained using some of the space for
metadata needs. Oracle ASM disks are the stor
age devices provisioned to an Oracle ASM
disk group and can be physical disk or partitions,
a Logical Unit Number (LUN) from a storage
array, a logical volume (LV), or a network-attached file. Each ASM disk is divided into many
ASM allocation units, the smallest contiguous amount of disk space that ASM allocates. When
you create an ASM disk group, you can set the ASM allocation unit size to 1, 2, 4, 8, 16, 32,
or 64 MB depending on the disk group compatib
ility level. One or more ASM allocation units
forms an ASM extent. An Oracle ASM extent is the raw storage used to hold the contents of
an Oracle ASM file. An Oracle ASM file consists
of one or more file extents. Variable extent
sizes of 1*AU size, 4*AU size, and 16*AU size are used for supporting very large ASM files
AC