Do you recommend the advance index compression for OLTP databases esp indexes of Enterprise Application databases (ERP,SAP,peoplesoft ,siebel) etc ]]>

Sorry, I don’t see the 2010 reference in the link ???

]]>this might be interesting, someone coping from your blog to his blog :). 2010’s info as 2014’s :))

Thanks John

]]>Thanks

Ajay

Very easily, considering how much the Oracle database keeps changing and improving over the years :)

]]>Wow, I have really fond memories of the class in Brussels as the Grand Place is truly one of the most beautiful places I have ever visited !!

]]>Oracle takes the maximum (or minimum) known value for a column and compares this with the required data is see if it’s outside the known range.

It then determines how far past the known range by comparing this to the full range (both min and max) and determines by what percentage it exceeds the listed full range.

So simplistically, if we have a min value of 0 and a max of 100 and we search for a value of say 142, this is outside of the known value and it’s out by a factor of some 42% of the full range of known values. So Oracle reduces the selectivity by 42% when determining how many rows will likely be returned. So the further out you are from the known range of values, the more the estimate is reduced until you are out by the full range of known values when Oracle now begins assume no rows are returned.

So if you don’t update your stats, and the min/max values become more and more stale, then the less and less the CBO will assume will actually be returned over time. Fine if indeed true, perhaps not so good if not true.

]]>Looks like you found the reference. Here’s a link for any visitors:

http://docs.oracle.com/database/121/DBLIC/editions.htm#CJACGHEB

The decision on how all these things get licensed is way way above my humble pay-scale :)

]]>Thanks for sharing your knowledge !

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