接手了一个新交接的库，alert日志频繁报告log file switch (checkpoint incomplete)事件
oracle文档解释：
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:APPADMINISTRATORORADATAYBREDO03.LOG NO
2 ONLINE D:APPADMINISTRATORORADATAYBREDO02.LOG NO
1 ONLINE D:APPADMINISTRATORORADATAYBREDO01.LOG NO
SQL>
查看切换频率:
SQL> select completion_time from v$archived_log order by 1 desc;
发现在系统繁忙时候，日志一分钟会切换好几次。
解决方案：
添加个日志组并将日志大小调整为100m
alter database add logfile group 4 ('D:APPADMINISTRATORORADATAYBREDO04a.LOG ','D:APPADMINISTRATORORADATAYBREDO04b.LOG ') size 100M;
然后将其它三组redo日志的进行调整：删除已有日志组，然后重建（要将日志组调整到inactive状态后再操作）
alter database drop logfile group 3;
alter database add logfile group 3 ('D:APPADMINISTRATORORADATAYBREDO03a.LOG ','D:APPADMINISTRATORORADATAYBREDO03b.LOG ') size 100M;
...