Hi,

Thanks for reply.

But I still think, if a large table is ordered, even I run reorg, it won't take a lot of time, right?

Maybe I should search how reorg works in fact. :)

Best wishes,
Qin

**********************
*A climber to DBA*
**********************
----- Original Message -----
From: "hsteiner" <db2udbdba-ezmlmshield-x45578342.[Email address protected]
To: "LazyDBA Discussion" <[Email address protected]
Sent: Monday, August 28, 2006 10:55 PM
Subject: Re: Is reorgchk necessary


> REORG can be a time and resource consuming job on a large table, so doing it selectively (based on REORGCHK results) makes sense. It will reorganize based on the "first" index created (typically the PK index) unless you specify a different index. I strongly recommend looking into REORGing by an index other than the PK - pick the index you do the most "set" processing on. For example, REORGing an employee table by deptcode will make deptcode set queries run much faster. When you are retrieving individual employee rows by a unique index, the index clustering doesn't really matter.
>
> RUNSTATS should *ALWAYS* follow a REORG, so your statistics accurately reflect the reorganized result.
>
> REBIND is a good idea so that your plans take advantage of the optimal strategy based on the REORG. For example, before the REORG the clusterratio of a certain index might have been poor, discouraging its use, but after the REORG your clusterratio might be 100% again, and the rebind would optimize accordingly.
>
> My 2 cents.
>
> Best, Hal Steiner
>
>
>
> -----Original Message-----
> From: db2udbdba-ezmlmshield-x63566171.[Email address protected]
> To: [Email address protected]
> Sent: Sun, 27 Aug 2006 9:45 AM
> Subject: Is reorgchk necessary
>
>
>
> Hi,
>
> As my understanding, reorg will physically move records in a table according the
> primary index sequence. So that durning the query, less IO operations are
> needed.
>
> reorgchk will generate a report accoding some statistic informations. It seems
> there will be a threshold. When this threshold reaches, it will mark the table
> or index with a * to tell reorg is necessary.
>
> But from my point of view, doing reorg as frequently as possible is better. When
> disordered records accumulate to a certain degree, it will cost longer time to
> run reorg. It just likes if you sort your book once a week or once a month.
>
> So I think reorg should be perfrom in spite of the result of reorgchk. If a
> table is ordered, "reorg" won't move any records. It works only when a table is
> disordered. Besides, reorgchk itself costs time to generate the report.
>
> Following is my preferred Database Maintenance Process:
>
> reorg --> runstats -> rebind
>
> I'm also not clear about the reorg on index. Since there can be only one primary
> index for one table, so the records can sort according only one sequence. What
> will the reorg of index do? Sort the index itself but not records in the table?
>
> Please feel free to correct me if you find any issues. And any comments will be
> greatly appreciated.
>
> Best wishes,
> Qin
>
> **********************
> *A climber to DBA*
> **********************
>
>
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