For performance reasons, the Oracle Database does not populate these views immediately when the actual modifications occur.
Run the FLUSH_DATABASE_MONITORING_INFO procedure in the DIMS_STATS PL/SQL package to populate these views with the latest information.
Posts under ‘dbms_stats’
exec FLUSH DATABASE MONITORING INFO;
Gather Statistics with DBMS_STATS by Jeff
Gather Statistics with DBMS_STATS
Automatic Statistics Gathering scheduler job
在Oracle10g中引入的优化器统计信息（Optimizer Statistics）自动收集，是一个看上去很不错的功能，但是在实际应用中却往往没有起到相应的效果，甚至在某些系统中我们会建议禁用这个功能。
10g dbms_stats
10g dbms_stats