RE: Documentation contradiction?

From: Singla, Sanjeev K. <SSingla_at_oxhp.com>
Date: Wed, 9 Aug 2000 10:53:28 -0400
Message-Id: <10584.114178@fatcity.com>

This is absolutely true. But u have to evaluate the usage. If u have 1000 users
hitting the same table and use the index everytime before it goes to the actual
table u are over-hitting the disk everytime for index as well as tablescan. Even if u have more disks in same tablespace u have no control on placement of
table and index segments. They may be poining to the same disk. By spreading the two u ensure that the disk is not hot. This will give u the maximum
life of the disk. Which further ensures the availability of the table which is more
important than index which is always recreatable.

Hope it helps.
Sanjeev

-----Original Message-----

From: O'Neill, Sean [mailto:Sean.ONeill_at_organon.ie] Sent: Wednesday, August 09, 2000 11:06 AM To: Multiple recipients of list ORACLE-L Subject: Documentation contradiction?

Hi Folks,

These excerpts from Oracle 8i documentation "appear" to be in contradiction to me. Seperate data and indexes on separate drives or not!. Am I correct or confusing apples and oranges so-to-speak.

Separating Tables and Indexes

It is not necessary to separate a frequently used table from its index. During the course of a transaction, the index is read first, and then the table is read. Because these I/Os occur sequentially, the table and index can be stored on the same disk without contention.

from
Oracle8i Tuning
Release 8.1.5
A67775-01
20
Tuning I/O

Place Datafiles Appropriately

Tablespace location is determined by the physical location of the datafiles that constitute that tablespace. Use the hardware resources of your computer appropriately.

For example, if several disk drives are available to store the database, it might be helpful to store table data in a tablespace on one disk drive, and index data in a tablespace on another disk drive. This way, when users query table information, both disk drives can work simultaneously, retrieving table and index data at the same time.

from
Administrator's Guide
Release 8.1.5
A67772-01
10
Managing Datafiles

Sean :)

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-- 
Author: O'Neill, Sean
  INET: Sean.ONeill_at_organon.ie

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Received on Wed Aug 09 2000 - 09:53:28 CDT