I had a similar situation once working in a data warehouse environment.
One example is a job that recreated a large dimension table each night:
The dimension table was truncated and reconstructed in phases - this was by
far the most efficient approach. It was necessary to analyze the table
part way through the building phase though. Doing analyze at this
particular point provided a massive performance increase. We could have
probably worked around it with hints but it was easier to just analyze the
table at particular points within the build script. A quick estimate was
all that was required and the couple of seconds spend analyzing could shave
maybe 30 minutes off the execution time. A final estimate at the end of
the batch meant that the stats were then valid until the next time the
table was rebuilt.
"Whittle Jerome
Contr NCI" To: Multiple recipients of list
ORACLE-L <[EMAIL PROTECTED]>
<[EMAIL PROTECTED] cc:
ott.af.mil> Subject: RE: Should we stop
analyzing?
Sent by:
[EMAIL PROTECTED]
com
31/12/2003 03:09
Please respond to
ORACLE-L
I'll see your 'analyzed every 4 hours' and raise you one. We have some
tables that are analyzed every time they are used! They are 'work' tables
that are sometimes empty, very full, or somewhere in between. Running
something when the statistics say the table is full but actually is empty
takes a little longer when CBO says use indexes; however, if CBO thinks the
table is empty and does a FTS when there's actually a million records, well
let's just say it takes a while. Hints work sometimes; however, analyzing
these table after they are populated and letting CBO do it's job usually
works best.
Two points.
First this particular database had not been analyzed for over a year when I
got there and this database gets larger daily. They added indexes but it
didn't make much difference. After analyzing, most things were much faster;
however, the 'work' tables started acting up depending on their state when
analyzed. We now analyze twice a month.
Second when it comes to these 'work' tables, I wasn't there and it wasn't
my idea!
Jerry Whittle
ASIFICS DBA
NCI Information Systems Inc.
[EMAIL PROTECTED]
618-622-4145
-----Original Message-----
From: Rachel Carmichael [SMTP:[EMAIL PROTECTED]
I have you beat.... one schema in one of our databases (9.2.0.2) is
analyzed every 4 hours. Not mine, and I *will* be talking to the DBA
about his reasoning...
however Jonathan's point may well be the reason. This is an
ever-growing database, frequent insert and updates, and sequences are
used throughout.
Analyze is "estimate" at least.
--- "Jamadagni, Rajendra" <[EMAIL PROTECTED]> wrote:
> Mogens, if you are looking for a poster boy ...
>
> We analyze 9 production databases ... *every day*.
> Raj
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