12carchive_lag_targe强制日志切换

12c R1测试环境

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ARCHIVE_LAG_TARGET forces a log switch after the specified amount of time elapses.

A 0 value disables the time-based thread advance feature; otherwise, the value represents the number of seconds. Values larger than 7200 seconds are not of much use in maintaining a reasonable lag in the standby database. The typical, or recommended value is 1800 (30 minutes). Extremely low values can result in frequent log switches, which could degrade performance; such values can also make the archiver process too busy to archive the continuously generated logs.
建议半个小时到1个小时切换一次，以下为了做实验测试，设置了60秒。

SQL> show parameter lag

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
archive_lag_target                   integer     0
client_result_cache_lag              big integer 3000
plsql_ccflags                        string
SQL> alter system set archive_lag_target=60;  --单位秒

System altered.

SQL> show parameter archive_lag_target;

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
archive_lag_target                   integer     60

SQL> select name,COMPLETION_TIME from v$archived_log where name is not null order by COMPLETION_TIME desc ;

NAME                                                         COMPLETION_TIME
------------------------------------------------------------ -------------------
+DATADG/arch/log_1_406_961866198_585bafa7.arc                2018-01-25 12-04-59
+DATADG/arch/log_1_405_961866198_585bafa7.arc                2018-01-25 12-03-59
...................省略

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