檢視oracle的redo日誌組切換頻率

檢視Oracle的redo日誌切換頻率：

單位：分鐘

第一種：

select * from v$log　a　where a.THREAD# = 1 ;

set line 200

select b.SEQUENCE#, b.FIRST_TIME,a.SEQUENCE#,a.FIRST_TIME,round(((a.FIRST_TIME-b.FIRST_TIME)*24)*60,2) from v$log_history a, v$log_history b where a.SEQUENCE#=b.SEQUENCE#+1 and b.THREAD#=1 order by a.SEQUENCE# desc;

第二種：

set line 200

select sequence#,first_time,nexttime,round(((first_time-nexttime)*24)*60,2) diff from (select sequence#,first_time,lag(first_time) over(order by sequence#) nexttime from v$log_history where thread#=1) order by sequence# desc;

看你的redo日誌大小。
Oracle給的建議是一般15-20分鐘左右，要根據資料量來判斷，最長時間（單位時間內資料量最少）維持在25-30分鐘，最好不要超過30分鐘。最短時間（單位時間內資料量最大），保持在10分鐘以上。

SELECT  trunc(first_time) "Date",

        to_char(first_time, 'Dy') "Day",

        count(1) "Total",

        SUM(decode(to_char(first_time, 'hh24'),'00',1,0)) "h0",

        SUM(decode(to_char(first_time, 'hh24'),'01',1,0)) "h1",

        SUM(decode(to_char(first_time, 'hh24'),'02',1,0)) "h2",

        SUM(decode(to_char(first_time, 'hh24'),'03',1,0)) "h3",

        SUM(decode(to_char(first_time, 'hh24'),'04',1,0)) "h4",

        SUM(decode(to_char(first_time, 'hh24'),'05',1,0)) "h5",

        SUM(decode(to_char(first_time, 'hh24'),'06',1,0)) "h6",

        SUM(decode(to_char(first_time, 'hh24'),'07',1,0)) "h7",

        SUM(decode(to_char(first_time, 'hh24'),'08',1,0)) "h8",

        SUM(decode(to_char(first_time, 'hh24'),'09',1,0)) "h9",

        SUM(decode(to_char(first_time, 'hh24'),'10',1,0)) "h10",

        SUM(decode(to_char(first_time, 'hh24'),'11',1,0)) "h11",

        SUM(decode(to_char(first_time, 'hh24'),'12',1,0)) "h12",

        SUM(decode(to_char(first_time, 'hh24'),'13',1,0)) "h13",

        SUM(decode(to_char(first_time, 'hh24'),'14',1,0)) "h14",

        SUM(decode(to_char(first_time, 'hh24'),'15',1,0)) "h15",

        SUM(decode(to_char(first_time, 'hh24'),'16',1,0)) "h16",

        SUM(decode(to_char(first_time, 'hh24'),'17',1,0)) "h17",

        SUM(decode(to_char(first_time, 'hh24'),'18',1,0)) "h18",

        SUM(decode(to_char(first_time, 'hh24'),'19',1,0)) "h19",

        SUM(decode(to_char(first_time, 'hh24'),'20',1,0)) "h20",

        SUM(decode(to_char(first_time, 'hh24'),'21',1,0)) "h21",

        SUM(decode(to_char(first_time, 'hh24'),'22',1,0)) "h22",

        SUM(decode(to_char(first_time, 'hh24'),'23',1,0)) "h23"

FROM    V$log_history

group by trunc(first_time), to_char(first_time, 'Dy')

Order by 1