Explanation/Reference:
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 the appropriate 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.