在线修改错了log_archive_config后primary无法归档到DG

把log_archive_config参数修改成其它库的了（多窗口操作太危险啦！！！！！！！！！！），改回来后alter日志没保错，查看等待事件，发现一个“LNS ASYNC end of log”的等待事件的进程，目测是LNS相关的。查询spid,发现是ora_tt00_*的进程，查询v$process定位相关trace，发现有报错:

ASYNC ignored current log: KCCLENAL clear thread open

* 2018-03-24 16:52:30.140360 6843 krsw.c

Error in determining current logfile for thread 1

ASYNC ignored current log: KCCLENAL clear thread open

* 2018-03-24 16:52:30.186923 6843 krsw.c

Error in determining current logfile for thread 1

ASYNC ignored current log: KCCLENAL clear thread open

* 2018-03-24 16:52:30.188465 6843 krsw.c

Error in determining current logfile for thread 1

ASYNC ignored current log: KCCLENAL clear thread open

defer掉到远程的归档，发现没用（12.1的bug）。将log_archive_dest_3参数置空，等oracle将相关session回收后再设置回去，问题得到解决。