Does Oracle server try to allocate extents on five-block boundaries?

Hi!

I'm reading "Performance and Tuning" Student Guide for 8i.

In chapter 9 "Using Oracle Blocks Efficiently" said:

| Larger extents can improve performance slightly because the Oracle
| server can read one large extent from disk with fewer multiblock reads
| than are required to read many small extents. To avoid partial multiblock
| reads, set the extent size to a multiple of 5 *DB_FILE_MULTIBLOCK_READ_COUNT.
| Multiply by five because the Oracle server tries to allocate extents on five-block boundaries.
| By matching extent sizes to the I/O and space allocation sizes, the
| performance cost of having many extents in a segment is minimized.
| However, for a table that never has a full table scan operation, it makes no
| difference in terms of query performance whether the table has one extent
| or multiple extents.

I woudered about mentioned algorithm of "...allocating extents on fiveblock  boundaries". No mention about it in "Oracle Documentation Library, Release 8.1.7". Only good known principles of allocation for DMT with its "MINIMUM EXTENT" and LMT with its "UNIFORM SIZE" or "AUTOALLOCATE".
Same results when searching in Goggles.

My question is: is this principle discarded relating to 8.1.7 or I missing something?

Thank you!

Sergey Adamenko. Received on Sat Jun 14 2003 - 09:54:55 CDT