Re: Snapshot Refresh Process ??

From: <tday6_at_csc.com>
Date: Tue, 11 Sep 2001 07:22:14 -0700
Message-ID: <F001.003898A3.20010911060023@fatcity.com>

I'm interested in the cutover point. Our snapshots are set up with FORCE, which allows Oracle to choose between a FAST or a COMPLETE. But at what point does Oracle decide that it will be faster to do the complete? Does Oracle need to have the tables analyzed so that it has some statistics to work with? Obviously, I'm unclear on the whole thing.

                                                                                       
     
                    Tracy Rahmlow                                                      
     
                    <Tracy.Rahmlow        To:     Multiple recipients of list ORACLE-L 
     
                    @aexp.com>            <ORACLE-L_at_fatcity.com>                       
     
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                    root_at_fatcity.c        Subject:     Snapshot Refresh Process ??     
     
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                    09/11/2001                                                         
     
                    12:10 AM                                                           
     
                    Please respond                                                     
     
                    to ORACLE-L

At times it is faster to do a complete refresh of an oracle snapshot rather than an incremental (fast). My question is how do you know when to do the complete? For example, there are times when a user will run a conversion and
they may update 10% of the rows in the master table. If I do a fast refresh
it may take 4 hours but if I did a complete it takes 2 hours. I have not seen
a pattern in determing the breakeven point. For example, one table we may update 20% of the rows and the incremental is faster other times we update 5%
of the rows in a different table and the complete would have been an better option. (Don't quote me on the percentages, just trying to make a point) I
remember seeing a reference to this issue that it was addressed at ioug conference years ago, but I did not find anything there. So again the question: What factor(s) should be considered to determine which process(fast
or complete) will provide for a faster refresh for higher than normal updates
to a master table? Thanks

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Author: Tracy Rahmlow
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Received on Tue Sep 11 2001 - 09:22:14 CDT