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What is the meaning of Performance Warning: Redundant Index and Page Size too small

3 posts in General Discussion Last posting was on 2006-03-30 15:07:54.0Z
Fenix Posted on 2006-03-30 10:07:48.0Z
From: "Fenix" <sales@bbccable.com>
Newsgroups: ianywhere.public.general
Subject: What is the meaning of Performance Warning: Redundant Index and Page Size too small
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No time no post at this forum.

Recently, I had unloaded a Sybase 5.0x Database and reload it in a new
sybase 9.0 database.

After I run db9eng with new database, it displays two performance
warning --- Redundant Index in [Table_name] and Page Size too small for
[Database_name].

Although the database still works with the application, I want to know what
is the meaning of these two performances warning, what problem will they
cause, and how to solve it.

Thank you very much for the previous help.

Fenix.


Breck Carter [TeamSybase] Posted on 2006-03-30 13:16:00.0Z
From: "Breck Carter [TeamSybase]" <NOSPAM__bcarter@risingroad.com>
Newsgroups: ianywhere.public.general
Subject: Re: What is the meaning of Performance Warning: Redundant Index and Page Size too small
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A "redundant index" is one that is not necessary because some other
index exists on the same columns. For example, a UNIQUE index on the
same columns as exist in the PRIMARY KEY is completely useless since
the primary key index will be used for query optimization.

If the table has a large number of rows and/or there are a lot of
inserts and deletes, a redundant index will waste disk space and/or
CPU time.

You can use Foxhound to poke around in your schema looking for
redundant indexes, space used, etc:
http://www.risingroad.com/foxhound_beta_3.html

A too-small page size can really kill performance. Here is the rule of
thumb: For most databases 4K is the best, for some 8K is better, and
all the other choices are bad. You set the page size when the database
is created; here is a sample command file:

REM -e simple encryption
REM -p page size; e.g., 4096, 8192
REM -s use checksums when writing pages

"%ASANY9%\win32\dbinit.exe" -p 4096 -s ddd.db
PAUSE

For more information about performance and tuning, see the Help, and
my book
http://www.risingroad.com/SQL_Anywhere_Studio_9_Developers_Guide.html

Breck

On 30 Mar 2006 02:07:48 -0800, "Fenix" <sales@bbccable.com> wrote:

>No time no post at this forum.
>
>Recently, I had unloaded a Sybase 5.0x Database and reload it in a new
>sybase 9.0 database.
>
>After I run db9eng with new database, it displays two performance
>warning --- Redundant Index in [Table_name] and Page Size too small for
>[Database_name].
>
>Although the database still works with the application, I want to know what
>is the meaning of these two performances warning, what problem will they
>cause, and how to solve it.
>
>Thank you very much for the previous help.
>
>Fenix.
>

--
SQL Anywhere Studio 9 Developer's Guide
Buy the book: http://www.amazon.com/exec/obidos/ASIN/1556225067/risingroad-20
bcarter@risingroad.com
RisingRoad SQL Anywhere and MobiLink Professional Services
www.risingroad.com


"Chris Keating(iAnywhere Solutions)" <NoSpamPlease_k_e_a_t_i_n_g Posted on 2006-03-30 15:07:54.0Z
From: "Chris Keating(iAnywhere Solutions)" <NoSpamPlease_k_e_a_t_i_n_g@i_A_n_y_w_h_e_r_e.com>
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For duplicate indices, see
http://www.ianywhere.com/developer/technotes/sas_dup_index_msgs.html


--

Chris Keating
Sybase Adaptive Server Anywhere Professional Version 8

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