Re: want clarification from Oracle gurus regarding I/O

From: Jonathan Gennick <jonathan_at_gennick.com>
Date: 2000/05/25
Message-ID: <c6lqis0bilsbaar2376sq8ourlb5e57c7q@4ax.com>#1/1

It all depends on a lot of things. If you need to know for sure, then you should look at Oracle's SQL Trace functionality. It's documented in tuning manual. You can enable tracing, execute your query, and then see the actual number of I/Os in the trace report.

You may also be able to use the SQL*Plus autotrace feature. For example:

SQL> set autotrace on
SP2-0613: Unable to verify PLAN_TABLE format or existence SP2-0611: Error enabling EXPLAIN report
SQL> select * from dual;

D
-
X

Statistics

          0  recursive calls
          4  db block gets
          1  consistent gets
          0  physical reads
          0  redo size
        839  bytes sent via SQL*Net to client
        656  bytes received via SQL*Net from client
          4  SQL*Net roundtrips to/from client
          1  sorts (memory)
          0  sorts (disk)
          1  rows processed

In this example, the number of physical reads was zero probably because that row was already in the buffer cache.

Jonathan

jonathan_at_gennick.com
http://gennick.com
Brighten the Corner Where You Are

On Wed, 24 May 2000 18:37:13 GMT, suresh_joshi_at_my-deja.com wrote:

>I appreciate if someone give me exactly what oracle do process the
>UPDATE request and how many i/o will happens because of that
Received on Thu May 25 2000 - 00:00:00 CDT