Re: Index Question

For OLTP, one key factor is whether the index is in memory.

If you double the size of a primary key field from varchar2(15) to varchar2(30), there will probably not be any change for the header and branch blocks of the index -- if they were in memory before they'll probably still be in memory.

If the leaf blocks of the index used to be in memory most of the time, there will also probably be no change -- unless you actually store different, longer values in the fields of this column. If longer values are stored
(and presumably that's the case, since that's why you're bumping up the
column size) it will take more leaf blocks to store them, and you might find that memory space limitations cause fewer of the leaf blocks to stay in memory, not to mention that other blocks get pushed out.

Ultimately, this may be a moot point. If you need a larger column size for larger values, you don't have much of a choice.

-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.com
-- 
Author: Greg Moore
  INET: sqlgreg_at_pacbell.net

Fat City Network Services    -- (858) 538-5051  FAX: (858) 538-5051
San Diego, California        -- Public Internet access / Mailing Lists
--------------------------------------------------------------------
To REMOVE yourself from this mailing list, send an E-Mail message
to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in
the message BODY, include a line containing: UNSUB ORACLE-L


(or the name of mailing list you want to be removed from).  You may

also send the HELP command for other information (like subscribing).