Wolfgang Breitling wrote:
Wolfgang, when I do SELECT * FROM TABLE(DBMS_XPLAN.DISPLAY) it tells me that "CPU costing is ON, despitePatty,
are you sure that is the only thing that changed? From all I know, your system statistics are ignored by the CBO because mreadtim < sreadtim. That is at odds with the CBO's ground rules that scattered reads have to be more "expensive" than sequential reads.
Of course, cardinality is only one aspect of an index' statistics
-- Mladen Gogala Oracle DBA Ext. 121