确定联机重做日志的日志切换频率
在Oracle中，联机重做日志的日志切换事件可以手动发起，也可以因为某个联机日志组写满后自动发起。
为了更清晰的看到日志切换的情况，可以通过v$log_history查看到日志切换的历史频率。
具体的查询如下命令LOG所示：
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 |
[oracle@ora12c - allah:~]$ sqlplus / as sysdba SQL*Plus: Release 12.1.0.2.0 Production on Thu Nov 13 01:21:56 2014 Copyright (c) 1982, 2014, Oracle. All rights reserved. Connected to: Oracle Database 12c Enterprise Edition Release 12.1.0.2.0 - 64bit Production With the Partitioning, OLAP, Advanced Analytics and Real Application Testing options SQL> set pagesize 80 SQL> select to_char(first_time,'yyyy-mm-dd hh24:mi:ss') "First Time",count(*) "Switch Count" from v$log_history group by to_char(first_time,'yyyy-mm-dd hh24:mi:ss') order by 1; First Time Switch Count ------------------- ------------ 2014-10-27 23:44:22 1 2014-10-27 23:44:38 1 2014-10-27 23:44:48 1 2014-10-27 23:45:16 1 2014-10-27 23:47:22 1 2014-10-27 23:47:40 1 2014-10-27 23:48:49 1 2014-10-27 23:49:58 1 2014-10-28 22:00:34 1 2014-10-28 22:01:13 1 2014-10-28 22:01:52 1 2014-10-29 21:00:06 1 2014-11-03 18:53:08 1 2014-11-03 23:00:05 1 2014-11-05 22:00:41 1 2014-11-06 22:24:47 1 2014-11-07 01:01:46 1 2014-11-07 22:01:26 1 2014-11-09 23:01:36 1 2014-11-10 22:40:15 1 2014-11-11 02:00:03 1 2014-11-11 22:04:25 1 2014-11-12 08:00:38 1 2014-11-13 01:16:41 1 24 rows selected. SQL> select to_char(first_time,'yyyy-mm-dd hh24:mi') "First Time",count(*) "Switch Count" from v$log_history group by to_char(first_time,'yyyy-mm-dd hh24:mi') order by 1; First Time Switch Count ---------------- ------------ 2014-10-27 23:44 3 2014-10-27 23:45 1 2014-10-27 23:47 2 2014-10-27 23:48 1 2014-10-27 23:49 1 2014-10-28 22:00 1 2014-10-28 22:01 2 2014-10-29 21:00 1 2014-11-03 18:53 1 2014-11-03 23:00 1 2014-11-05 22:00 1 2014-11-06 22:24 1 2014-11-07 01:01 1 2014-11-07 22:01 1 2014-11-09 23:01 1 2014-11-10 22:40 1 2014-11-11 02:00 1 2014-11-11 22:04 1 2014-11-12 08:00 1 2014-11-13 01:16 1 20 rows selected. SQL> select to_char(first_time,'yyyy-mm-dd hh24') "First Time",count(*) "Switch Count" from v$log_history group by to_char(first_time,'yyyy-mm-dd hh24') order by 1; First Time Switch Count ------------- ------------ 2014-10-27 23 8 2014-10-28 22 3 2014-10-29 21 1 2014-11-03 18 1 2014-11-03 23 1 2014-11-05 22 1 2014-11-06 22 1 2014-11-07 01 1 2014-11-07 22 1 2014-11-09 23 1 2014-11-10 22 1 2014-11-11 02 1 2014-11-11 22 1 2014-11-12 08 1 2014-11-13 01 1 15 rows selected. SQL> |
如上所示，分别列出了秒、分、时三种时间间隔里，日志切换发生的频率信息。
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Ending。
