12c R1测试环境
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
