1. 查询数据库是否启用了force_logging
      su - oracle
      export ORACLE_SID=xxxx
      sqlplus “as sysdba
      select log_mode,force_logging from gv$database;

    2. 开启强制日志. 注: 尽量在业务低峰时开启
      alter database force logging;

      切换redo log, 每个节点都执行几次
      alter system switch logfile ;