I think Jonathan is correct when he says that index rebuilds are not often needed.
Tom Kyte states that they are never needed, which I don't believe to be correct.
I'll try to back this up with data in the future.
So if Tom asks any of you why you don't use automatic space management in
your LMT's, you can ask him why he doesn't use 'alter index rebuild'. ;)
Jared
| Yong Huang <[EMAIL PROTECTED]>
Sent by: [EMAIL PROTECTED] 11/06/2003 02:59 PM
|
To: Multiple recipients of list ORACLE-L <[EMAIL PROTECTED]> cc: Subject: Re: any problem rebuilding indexes used for replication |
renu (and Jared),
The reason I'm very interested in whether there's performance improvement is
that there's a thread on the newsgroup about index rebuild recently. See
http://groups.google.com/groups?threadm=pan.2003.11.03.08.09.24.330520%40RE-MO-VE.BountifulSolutions.co.uk
Jonathan Lewis says there's almost no need to rebuild indexes, although his
"Practical Oracle8i" lists at least one case you may benefit by rebuilding. (I
don't have the book with me). Asktom.oracle.com has numerous messages advising
against rebuilding indexes. Let's set theory aside for a moment and do the
experiment. Please post your report of performance change. Thanks.
Yong Huang
--- renu r <[EMAIL PROTECTED]> wrote:
> Jared : I think it is fragmented based on scripts and knowing that there have
> been lot of deletes.
>
> One script uses the table index_stats and looks at field del_lf_rows which
> should be less at least in comparison to field lf_rows. I mean less is good.
> more bad. I am not sure about the script but I will post it here if someone
> says so or send it to anyone if they want.
>
> I am sure the experts here know about it and can clarify if it is any good
> to look at the index_stats table.
>
> One other simple useful script is :
>
> SELECT owner, index_name, blevel
> FROM all_indexes
> WHERE blevel > 2
>
> This can be bacause the size of table is big so it is not definitive. I will
> check the level after rebuild.
>
> Benefits expected : Space savings (definitely). performance (hopefully). I
> will let you and Yong know about the benefits if any. If I get some help.
>
>
> [EMAIL PROTECTED] wrote:
>
> I'm curious, how have you identified the fragmentation?
>
> What benefits do you expect from the rebuild of the indexes?
>
> Are you targeting certain indexes that have been identified as
> benefiting from a rebuild, or just planning to rebuild all indexes?
>
> Jared
>
>
>
>
> renu r <[EMAIL PROTECTED]>
> Sent by: [EMAIL PROTECTED]
> 11/05/2003 06:14 PM
> Please respond to ORACLE-L
>
>
> To: Multiple recipients of list ORACLE-L
> <[EMAIL PROTECTED]>
> cc:
> Subject: any problem rebuilding indexes used for replication
>
>
> Hello,
> I have to rebuild some primary key indexes due to excessive fragmentation.
> It is rebuild not drop and create. We have multi master replication running.
> Is there any problem to replication if I do that. Has anyone tried it? TIA.
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