X$KFFXP and ASM Metadata - Secrets of the Oracle Database - page 123

Figure 12-1 depicts the mapping of block 21978 in extent 0 of the database segment LOCATIONS
to allocation unit 238 in the ASM disk. This block is 38 blocks past the first block in allocation
unit 238. Since the segment's extent consists of 8 blocks, the ASM allocation unit contains addi-
tional extents, possibly belonging to different segments.

RDBMS ASM

Block 21793

Extent 0 …

…
…
…
…
…

AU# 2
AU# 3
AU# 4

Block 21798

Extent 1

…
…

AU# 238

Disk

Extent 2

Segment

Figure 12-1. Mapping of a block in a database segment to a block within an allocation unit of an
ASM disk