Re: Separating data, index objects

From: DA Morgan <damorgan_at_psoug.org>
Date: Fri, 08 Jul 2005 01:07:33 -0700
Message-ID: <1120810061.980891@yasure>

Joel Garry wrote:

>>Actually there is no such thing as "all blocks contiguous." As amazing
>>as it may be many operating systems won't lay down a single file on a
>>clean drive that way.

>
>
> I think this is a red herring, as whatever it is, it appears to Oracle
> as contiguous, and if Oracle has to read more stuff, it makes no
> difference.

If RAW I would agree with you. But otherwise Oracle isn't doing the reading.

>>We could talk about RAW but that is quite a different matter. And even
>>on your single user database ... there will be a substantial amount of
>>recursive SQL. In Oracle you are never alone.

>
> And heck, why not talk about raw? And why is there recursive SQL on a
> single table scan?

Didn't say there was. But Oracle will be running it in the background and issuing reads and writes that may very well get in the middle of what you, the end user, perceive to be a single read request.

You go to Oracle and say SELECT col1, col6 FROM t;

And whats the first thing that happens?

select /*+ rule */ bucket_cnt, row_cnt, cache_cnt, null_cnt, timestamp#, sample_size, minimum, maximum, distcnt, lowval, hival, density, col#, spare1, spare2, avgcln from hist_head$ where obj#=:1 and intcol#=:2;

And it has two indexes that I can guarantee you are in the SYSTEM tablespace.

In Oracle you are never alone. Even on a single user system.

-- 
Daniel A. Morgan
http://www.psoug.org
damorgan_at_x.washington.edu
(replace x with u to respond)

Received on Fri Jul 08 2005 - 03:07:33 CDT