1. 在使用DBLINK連接遠程DB之前，確認是否安全，防止SCN大量跳躍，導致headroom過小。

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select

((((

((to_number(to_char(cur_date,'YYYY'))-1988)*12*31*24*60*60) +

((to_number(to_char(cur_date,'MM'))-1)*31*24*60*60) +

(((to_number(to_char(cur_date,'DD'))-1))*24*60*60) +

(to_number(to_char(cur_date,'HH24'))*60*60) +

(to_number(to_char(cur_date,'MI'))*60) +

(to_number(to_char(cur_date,'SS')))

) * (16*1024)) - &target_db_scn) --跳躍目標值的10進制，看看跳躍到這個數還能剩多少天

/ (16*1024*60*60*24)

) headroom

from (select sysdate cur_date from dual);

2.查詢headroom

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SELECT SYSDATE sdate,

???????'Headroom',

???????ROUND ( (chk16kscn - gscn) / 3600 / 16 / 1024, 1) AS headroom_value

??FROM (SELECT tim,

???????????????gscn,

???????????????rate,

???????????????delta,

???????????????( ( ( (TO_NUMBER (TO_CHAR (tim, 'YYYY')) - 1988)

??????????????????????* 12

??????????????????????* 31

??????????????????????* 24

??????????????????????* 60

??????????????????????* 60)

???????????????????+ ( (TO_NUMBER (TO_CHAR (tim, 'MM')) - 1)

??????????????????????* 31

??????????????????????* 24

??????????????????????* 60

??????????????????????* 60)

???????????????????+ ( ( (TO_NUMBER (TO_CHAR (tim, 'DD')) - 1))

??????????????????????* 24

??????????????????????* 60

??????????????????????* 60)

???????????????????+ (TO_NUMBER (TO_CHAR (tim, 'HH24')) * 60 * 60)

???????????????????+ (TO_NUMBER (TO_CHAR (tim, 'MI')) * 60)

???????????????????+ (TO_NUMBER (TO_CHAR (tim, 'SS'))))

????????????????* (16 * 1024))

??????????????????chk16kscn

??????????FROM (SELECT FIRST_TIME tim,

???????????????????????(next_time - first_time) * 24 * 60 * 60 delta,

???????????????????????FIRST_CHANGE# gscn,

???????????????????????( (NEXT_CHANGE# - FIRST_CHANGE#)

????????????????????????/ ( (NEXT_TIME - FIRST_TIME) * 24 * 60 * 60))

??????????????????????????rate

??????????????????FROM v$archived_log

???????????????????WHERE (next_time > first_time))

????????ORDER BY 1 DESC)

?WHERE TO_CHAR (tim, 'YYYY/MM/DD HH24') >

??????????????TO_CHAR (SYSDATE - 1, 'YYYY/MM/DD HH24')

???????AND ROWNUM < 2

來自 “ ITPUB博客 ” ，鏈接：http://blog.itpub.net/15412087/viewspace-2157232/，如需轉載，請注明出處，否則將追究法律責任。

轉載于:http://blog.itpub.net/15412087/viewspace-2157232/

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