Active Session History (ASH) performed an emergency flush

告警日志信息
Tue Sep 15 14:29:27 2015
Active Session History (ASH) performed an emergency flush. This may mean that ASH is undersized. If emergency flushes are a recurring issue, you may consider increasing ASH size by setting the value of _ASH_SIZE to a sufficiently large value. Currently, ASH size is 67108864 bytes. Both ASH size and the total number of emergency flushes since instance startup can be monitored by running the following query:
select total_size,awr_flush_emergency_count from v$ash_info;

执行告警日志中查询语句
SYS@hkprdbuat> select total_size/1024/1024 MB,awr_flush_emergency_count from v$ash_info;

MB AWR_FLUSH_EMERGENCY_COUNT
---------- -------------------------
64 3

查询当前大小
select x.ksppinm name,y.ksppstvl value,y.ksppstdf isdefault,decode(bitand(y.ksppstvf,7),1,'MODIFIED',4,'SYSTEM_MOD','FALSE') ismod,
decode(bitand(y.ksppstvf,2),2,'TRUE','FALSE') isadj
from sys.x$ksppi x,sys.x$ksppcv y
where x.inst_id = userenv('Instance') and
y.inst_id = userenv('Instance') and
x.indx = y.indx and
x.ksppinm ='_ash_size'
order by translate(x.ksppinm, ' _', ' ');

NAME VALUE ISDEFAULT ISMOD ISADJ
---------- ---------- ---------- ---------- ----------
_ash_size 1048618 TRUE FALSE FALSE

修改大小为100M
alter system set "_ash_size"=100M;

再次查询
select x.ksppinm name,y.ksppstvl value,y.ksppstdf isdefault,decode(bitand(y.ksppstvf,7),1,'MODIFIED',4,'SYSTEM_MOD','FALSE') ismod,
decode(bitand(y.ksppstvf,2),2,'TRUE','FALSE') isadj
from sys.x$ksppi x,sys.x$ksppcv y
where x.inst_id = userenv('Instance') and
y.inst_id = userenv('Instance') and
x.indx = y.indx and
x.ksppinm ='_ash_size'
order by translate(x.ksppinm, ' _', ' ');

NAME VALUE ISDEFAULT ISMOD ISADJ
---------- ---------- ---------- ---------- ----------
_ash_size 104857600 TRUE SYSTEM_MOD FALSE

告警日志信息
Tue Sep 15 15:03:25 2015
ALTER SYSTEM SET _ash_size='100M' SCOPE=BOTH;

吕星昊
2015.9.15

ITPub博客

Active Session History (ASH) performed an emergency flush

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