问题描述：oracle log file switch (checkpoint incomplete)，Every 15 min, tpm will drop to almost zero. cpu负载不高，很低。
1 set the parameter :
ALTER SYSTEM SET log_checkpoint_interval=20000 SCOPE=BOTH;
#没有解决掉
2 生成@?/rdbms/admin/awrrpt.sql 报告
-- see SQL ordered by Elapsed Time
-- SQL Statistics
-- see the cpu
select ash.sql_id,
sum(decode(ash.session_state,'ON CPU',1,0)) "CPU",
sum(decode(ash.session_state,'WAITING',1,0)) -
sum(decode(ash.session_state,'WAITING',decode(en.wait_class,'USER I/O',1,0),0)) "WAIT",
sum(decode(ash.session_state,'WAITING',decode(en.wait_class,'USER I/O',1,0),0))
"IO",
sum(decode(ash.session_state,'ON CPU',1,1)) "TOTAL"
from v$active_session_history ash,v$event_name en
where SQL_ID is not null and en.event#=ash.event# and ash.sample_time > sysdate -1/(24*60)
group by ash.sql_id
order by sum(decode(ash.session_state,'ON CPU',1,1)) desc;
拿到执行的SQL,baidu之，google之，发现很多人都说redo需要加大。
3 see redo logs
select * from vlog;select∗fromvlogfile; 为300M，大家推荐的为1G以下，还有调整的空间。
4 add new redo logs 添加新的redo log组
alter database add logfile thread 1 group 6 ('/opt/app/product/11.2/oradata/novadb/redo16.log') size 600M;
alter database add logfile thread 1 group 7 ('/opt/app/product/11.2/oradata/novadb/redo17.log') size 600M;
alter database add logfile thread 1 group 8 ('/opt/app/product/11.2/oradata/novadb/redo18.log') size 600M;
alter database add logfile thread 1 group 9 ('/opt/app/product/11.2/oradata/novadb/redo19.log') size 600M;
alter database add logfile thread 1 group 10 ('/opt/app/product/11.2/oradata/novadb/redo20.log') size 600M;
5 see the new logs
5.1 see the status
SQL> select status,GROUP# from v$log;
STATUS GROUP#
------------------------------------------------ ----------
ACTIVE 1
ACTIVE 2
ACTIVE 3
CURRENT 4
ACTIVE 5
ACTIVE 6
ACTIVE 7
ACTIVE 8
ACTIVE 9
ACTIVE 10
10 rows selected.
5.2 see the log file directory
SQL> select member,GROUP# from v$logfile;
MEMBER
--------------------------------------------------------------------------------
GROUP#
----------
/opt/app/product/11.2/oradata/novadb/redo06.log
1
/opt/app/product/11.2/oradata/novadb/redo01.log
2
/opt/app/product/11.2/oradata/novadb/redo03.log
3
MEMBER
--------------------------------------------------------------------------------
GROUP#
----------
/opt/app/product/11.2/oradata/novadb/redo16.log
6
/opt/app/product/11.2/oradata/novadb/redo17.log
7
/opt/app/product/11.2/oradata/novadb/redo18.log
8
MEMBER
--------------------------------------------------------------------------------
GROUP#
----------
/opt/app/product/11.2/oradata/novadb/redo19.log
9
/opt/app/product/11.2/oradata/novadb/redo20.log
10
/opt/app/product/11.2/oradata/novadb/redo04.log
4
MEMBER
--------------------------------------------------------------------------------
GROUP#
----------
/opt/app/product/11.2/oradata/novadb/redo05.log
5
10 rows selected.
6 oracle can continue to use the old redo logs .
OK,每隔15分钟，oracle并发800/秒的时候，应用卡住的现象没有了。