Allocation Units (AU)
Every ASM disk is divided into allocation units (AU).
The AU is the fundamental allocation unit on an ASM disk.
A
file extent consists of one or more AUs, a file consists of one or more file extents.
The size of the disk's AUs are set with the disk group attribute AU_SIZE. Possible values are 1, 2, 4, 8, 16, 32 or 64 MB.
Data warehouses and
OLAP environments tend to have larger AUs because they have large sequential reads.