1.查询数据库打开模式（备库）
SQL> select open_mode from v$database; OPEN_MODE -------------------- READ ONLY WITH APPLY
当数据库显示以上状态时，说明实时查询已开启
2.步骤1中的状态不一定是实时同步的状态，要开启实时同步，需以下动作
SQL> recover managed standby database cancel; Media recovery complete. SQL> select open_mode from v$database; OPEN_MODE -------------------- READ ONLY SQL> alter database recover managed standby database using current logfile disconnect; Database altered. SQL> select open_mode from v$database; OPEN_MODE -------------------- READ ONLY WITH APPLY
原文：http://www.cnblogs.com/vijayfly/p/5091271.html