Which of these 3 operations creates the most volume of total REDO log
file entries; not REDO log *records*: INSERT, UPDATE, or DELETE? A
colleague of mine says INSERTS add more to the redo log file. His
rationale? the redo log contains all changes to the database; and an
entire row takes the most redo log file space to store and re-play if
the database goes down.

In practice, it seems like DELETEs create larger REDO log files; have
seen servers crash when archive redo log disk space runs out from
running DELETE FROMs instead of TRUNCATEs; when the same raw number of
INSERT operations doesn't seem to cause the same problem.

The only thing I can come up with: for UNDO, DELETE operations create
the most UNDO volume because they store the "before" image of a row.
INSERT operations create the least UNDO volume because they store only
a ROWID. Seems that UNDO records are mirrored in the redo log files.
Is this why large numbers of INSERTS seem to be less redo logfile
intensive than the same number of DELETEs?

Wondering if I'm missing something about a symmetry or asymmetry
between INSERTs and DELETEs and the volume of space they fill in the
redo log files; vs. redo records only.

Thanks.

Dana

On Jul 17, 12:39*pm, dana <dana_at_w... (AT) yahoo (DOT) com> wrote:
You're missing the concept of change vectors. The redo is the
difference between the block and the new block. If you only change a
varchar2(1), not much redo.

See:
http://download.oracle.com/docs/cd/B....htm#sthref857
http://orainternals.wordpress.com/20...gging-changes/
metalink Note: 1031381.6 or
http://advait.wordpress.com/2008/01/...-database-10g/

Google around, there are explanations by people like Tom Kyte
somewhere that compare how much redo generated.
http://asktom.oracle.com/pls/asktom/...:7036069421885
isn't what I was looking for, but a start.

jg
--
@home.com is bogus.
http://www3.signonsandiego.com/stori...&zIndex=133482

Thanks Joel