why the cardinality of explain plan defers with the caridnality in row source operation

Hello,

In my database environment for many of the queires the explain plan cardinality defers (huge difference) with the cardinality shown by row source operations of tkprof.
I have been trying to find all possible reasons -

so far I came to know that 2 main reasons -

1. limitation of cbo as mentioned in the link below

http://asktom.oracle.com/pls/asktom/f?p=100:11:0::::P11_QUESTION_ID:40230704959128

it also tells that solution is such cases is use dynamic_samping.

2. the other reason is poor stats on the undelying tables/indexes.

please add if there are any more.

also how to collect a good stats - is there any oracle recommendation - best practices ?

are the above 2 are only reasons or there are many more - i went to differnt forums and it seems that there are many more. please share if you have come across such sitution - possible solutions etc.

Thanks
Ajeet

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