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oracle sql running 4 times slows after truncate table, reload data, rebuild indexes

Posted on 2012-08-19
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Last Modified: 2012-08-20
Hi,

We truncated a table, dropped indexes, insert data back with 0.1% new data, rebuild indexes,
analyzed table estimate 33%. But our sqls based on this table run about at least 4  times slower , some of them hung there. Did we miss a step?

Please advise ASAP.

Thanks,

Luchuan
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Question by:luchuanc
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by:lwadwell
lwadwell earned 500 total points
ID: 38309429
Did you happen to capture the explain plans for the SQL's before the truncate etc.?  With a change in the table size with the new stats ... the explain plans may have shifted so having the reference point to prior the change can help analyse the problem.
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by:luchuanc
ID: 38309472
No before explain plan
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sdstuber earned 500 total points
ID: 38309979
How did you gather stats?  What was the exact command?
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LVL 38

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by:Geert Gruwez
Geert Gruwez earned 500 total points
ID: 38310689
did you reuse or drop the storage
with reuse, you may have a loft of "unused" space in the table

if the table is currently in tablespace A

alter table move tablespace B;
alter table move tablespace A;

this should shrink the table to the correct size
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by:slightwv (䄆 Netminder)
slightwv (䄆 Netminder) earned 500 total points
ID: 38311330
It's also possible the 33% estimate was not enough to get a valid representation of the data.

Can you post the current execution plan?
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Author Closing Comment

by:luchuanc
ID: 38311860
Hi All,

We ran the following command the that seems resolved the problem:
exec dbms_stats.gather_table_stats('AXIUM','HISTORY', estimate_percent=>20, method_opt=>'FOR ALL COLUMNS SIZE 1', cascade=>true);

Thanks a lot,

Luchuan
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Expert Comment

by:sdstuber
ID: 38311963
20% is really big

if you're going to sample such a large portion of the table, you're probably better off doing a full compute (NULL) rather than estimate.

my guess is the first time you didn't have cascade so the indexes were missed
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