Re: Direct IO

From: Jonathan Lewis <jonathan_at_jlcomp.demon.co.uk>
Date: Sun, 24 Jun 2001 06:32:47 +0100
Message-ID: <993360585.466.0.nnrp-12.9e984b29@news.demon.co.uk>

In an Oracle context, Direct I/O usually refers to the 'direct read' and 'direct write' activity that Oracle employs to bypass its own
db_block_buffer_cache. This feature can be used in:

    sort operations
    parallel scans
    LOB handling
    direct path inserts

and probably CTAS and Create Index, though I haven't actually checked those.

--
Jonathan Lewis

Host to The Co-operative Oracle Users' FAQ
http://www.jlcomp.demon.co.uk/faq/ind_faq.html

Author of:
Practical Oracle 8i: Building Efficient Databases
See http://www.jlcomp.demon.co.uk/book_rev.html

Seminars on getting the best out of Oracle
See http://www.jlcomp.demon.co.uk/seminar.html






Dave Haas wrote in message ...


>Hi.

>

>I have a question with regard to terminology.  In several posts (and an

>argument I had with Howard a while ago :) people have used the term 'Direct

>IO'.  To be perfectly honest I'm not exactly sure what that means.  AFAIK

>the IO options are 1) file-system buffered and 2) Raw IO.  I heard (or more

>to the point, read) a post that said something to the effect of '... direct

>I/O means that the buffer cache is not involved in the operation ...'.

 Does


>that have something to do with the sort-direct-write operation and the old

>SORT_WRITE_BUFFERS and SORT_WRITE_BUFFER_SIZE?  I'm a little confused (as

>usual) ...

>

>Dave

>

>

Received on Sun Jun 24 2001 - 00:32:47 CDT