接手了一個新交接的庫，alert日志頻繁報告log file switch (checkpoint incomplete)事件
oracle文檔解釋：
Waiting for a log switch because the session cannot wrap into the next log. Wrapping cannot be performed because the checkpoint for that log has not completed.
查看redo日志信息:
SQL> select * from v$log;
GROUP# THREAD# SEQUENCE# BYTES BLOCKSIZE MEMBERS ARCHIVED STATUS FIRST_CHANGE# FIRST_TIME NEXT_CHANGE# NEXT_TIME
---------- ---------- ---------- ---------- ---------- ---------- -------- ---------------- ------------- ----------- ------------ -----------
1 1 19852 52428800 512 1 YES INACTIVE 179403613 7/27/2015 1 179417290 7/27/2015 1
2 1 19853 52428800 512 1 NO CURRENT 179417290 7/27/2015 1 281474976710
3 1 19851 52428800 512 1 YES INACTIVE 179393208 7/27/2015 1 179403613 7/27/2015 1
SQL> select * from v$logfile;
GROUP# STATUS TYPE MEMBER IS_RECOVERY_DEST_FILE
---------- ------- ------- -------------------------------------------------------------------------------- ---------------------
3 ONLINE D:\APP\ADMINISTRATOR\ORADATA\YB\REDO03.LOG NO
2 ONLINE D:\APP\ADMINISTRATOR\ORADATA\YB\REDO02.LOG NO
1 ONLINE D:\APP\ADMINISTRATOR\ORADATA\YB\REDO01.LOG NO
SQL>
查看切換頻率:
SQL> select completion_time from v$archived_log order by 1 desc;
發現在系統繁忙時候，日志一分鍾會切換好幾次。
解決方案：
添加個日志組並將日志大小調整為100m
alter database add logfile group 4 ('D:\APP\ADMINISTRATOR\ORADATA\YB\REDO04a.LOG ','D:\APP\ADMINISTRATOR\ORADATA\YB\REDO04b.LOG ') size 100M;
然后將其它三組redo日志的進行調整：刪除已有日志組，然后重建（要將日志組調整到inactive狀態后再操作）
alter database drop logfile group 3;
alter database add logfile group 3 ('D:\APP\ADMINISTRATOR\ORADATA\YB\REDO03a.LOG ','D:\APP\ADMINISTRATOR\ORADATA\YB\REDO03b.LOG ') size 100M;
...