log file switch (checkpoint incomplete)

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:\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:\APP\ADMINISTRATOR\ORADATA\YB\REDO04a.LOG ','D:\APP\ADMINISTRATOR\ORADATA\YB\REDO04b.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:\APP\ADMINISTRATOR\ORADATA\YB\REDO03a.LOG ','D:\APP\ADMINISTRATOR\ORADATA\YB\REDO03b.LOG ') size 100M;

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