索引访问与全表扫描的代价比例(百分比)
DSS\数据仓库可调整为50
SELECT EVENT,AVERAGE_WAIT FROM V$SYSTEM_EVENT
WHERE EVENT LIKE ‘db file s%’;
EVENT AVERAGE_WAITS
========================= ==============
db file sequential reads .33178629
db file scattered reads 2.190087
.33178629/2.190087
------------------
.151494571)
设置OPTIMIZER_INDEX_COST_ADJ =15.