使用statspack进行oracle性能分析

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在做运行报告的时候，主机可以取CPU，内存，进程数的相关参数做报表，而数据库却很难做出长时间性能参数的报告。Statspack是oracle性能分析的一个报告，但这个报告只能取一个规定时间段的值，可以用来分析问题，但不能反映随时间的变化趋势，也很难进行图表展示。

Oracle相关工具toad提供了statspack的简单图表展示，但选择时间点很麻烦，且只有有限几个参数。原则上来说，工具能实现的功能利用sql语句都能实现。下面是一个利用statspack进行oracle性能分析的一个简单例子。

具体sql语句如下

select w.snap_id, sn.SNAP_TIME, w.event event, w.total_waits - w.last_wait waits, w.total_timeouts - w.last_timeout timeouts, (w.time_waited - w.last_time_waited)/1000000 time_waited_S from perfstat.stats$snapshot sn, (select snap_id, dbid, instance_number, event, total_waits, lag(total_waits, 1) over (order by event, snap_id) last_wait, total_timeouts, lag(total_timeouts, 1) over (order by event, snap_id) last_timeout, time_waited_micro time_waited, lag(time_waited_micro, 1) over (order by event, snap_id) last_time_waited from perfstat.stats$system_event where event not in (select event from perfstat.stats$IDLE_EVENT) and snap_id in (select snap_id from stats$snapshot where snap_time >sysdate -300) ----300 days ) w where w.time_waited - w.last_time_waited > 0 and w.snap_id > (select min(snap_id) from stats$snapshot where snap_time >sysdate -300) ----300 days --and SN.snap_id in (22391,22392,22393) and sn.snap_id = w.snap_id and sn.dbid = w.dbid and sn.instance_number = w.instance_number and event not like '%message%' and event not like 'SQL*Net%' and (w.time_waited - w.last_time_waited) > 600*1000000 ---- wait time >10 min UNION ALL select ss.snap_id, sn.SNAP_TIME, 'CPU TIME' ,0, 0,ROUND((ss.value - lag(ss.value,1) over (order by ss.snap_id))/100,0) as value_cputime from perfstat.stats$sysstat ss, perfstat.stats$snapshot sn where ss.snap_id = sn.snap_id and ss.name = 'CPU used by this session' and ss.snap_id in (select snap_id from stats$snapshot where snap_time >sysdate -300) --and ss.snap_id in (22391,22392,22393) and ss.dbid = sn.dbid and ss.instance_number = sn.instance_number order by 1, 6 desc

通过sql查询出来的数据，导入到excel中（可以利用taod、pl/sql等工具），利用excel的透视图功能，进行图形绘制，如下图是某系统2011年1月的top wait event的结果。从图可以看出主要等待事件是db file sequential read和cpu time。db file sequentialread事件多说明系统IO压力大。

命中率的图（本周），低点一般在凌晨4点，其它命中率98%以上

理论上讲，statspack报告中的所有性能参数都可以进行图表展示，前提是拥有定期收集的数据。