monitoring usage

1. Which two statements are true about identifying unused indexes? (Choose two.)

A. Performance is improved by eliminating unnecessary overhead during DML operations.

B. V$INDEX_STATS displays statistics that are gathered when using the MONITORING USAGE keyword.

C. Each time the MONITORING USAGE clause is specified, the V$OBJECT_USAGE view is reset for the specified index.

D. Each time the MONITORING USAGE clause is specified, a new monitoring start time is recorded in the alert log.

 

参照以下BLOG,理解如何查看索引监控的使用以及注意事项:

(1)http://ora110.itpub.net/post/33978/457118

(2)http://www.eygle.com/archives/2004/12/monitor_index_usage.html

 

答案:AC

解释:

A:在DML操作中消除不必要的消耗使性能得到提升

B:V$INDEX_STATS 视图显示使用MONITORING USAGE 关键字获得的统计信息,应该是V$OBJECT_USAGE

C:每次开始MONITORING USAGE 语句将重置V$OBJECT_USAGE 视图的相应索引信息

D:每次开始MONITORING USAGE 语句,一个新的监控开始时间被记录到ALERT LOG中,没有记录,可以查看ALERT_<SID>.LOG系统日志文件

 

总结:

开始监视索引使用:ALTER INDEX 索引名 MONITORING USAGE;

查看被监视索引使用情况:SELECT * FROM V$OBJECT_USAGE;

停止监视索引使用:ALTER INDEX 索引名 NOMONITORING USAGE;