Hi! > UNIQUE SCAN followed by a TABLE ACCESS BY ROWID. Well, how big is the = > index? How many levels? Remember that regardless of the value = > specified in the pk_column predicate, the number of levels from the = > index root block to any leaf block is always the same. So, if the index = > has a BELVEL of, say, 3, then to get from the root to the leaf = > containing 123 will be 4 buffer gets. The TABLE ACCESS BY ROWID is one = > more buffer get. So, that's a total of 5 buffer gets. =20 Also, the LIO count may increase when Oracle has to construct a read consistent clone of index/datablocks... Tanel. ---------------------------------------------------------------- Please see the official ORACLE-L FAQ: http://www.orafaq.com ---------------------------------------------------------------- To unsubscribe send email to: oracle-l-request@xxxxxxxxxxxxx put 'unsubscribe' in the subject line. -- Archives are at //www.freelists.org/archives/oracle-l/ FAQ is at //www.freelists.org/help/fom-serve/cache/1.html -----------------------------------------------------------------