--查询日志的切换频率
select t1.RECID as srecid
,t2.RECID as erecid
,t1.FIRST_TIME as stime
,t2.FIRST_TIME as etime
,round((t2.FIRST_TIME-t1.FIRST_TIME)*1440,2) as minutes
from v$log_history t1,v$log_history t2
where t1.RECID+1=t2.RECID and /*选择时间段*/t1.FIRST_TIME between trunc(sysdate)/*起始*/ and sysdate/*终止*/
order by t1.RECID desc