PING[ARC2]: Heartbeat failed to connect to standby 'gqtzdb_dg'. Error is 16047

　　Data Guard搭建完畢之后，執行開啟歸檔路徑2，結果發現不同步，

SQL> alter system set log_archive_dest_state_2=enable;

　　查看錯誤日志，發現有PING[ARC2]: Heartbeat failed to connect to standby 'gqtzdb_dg'. Error is 16047.的報錯：

[oracle@KG-ORA-01 trace]$ tail -100f alert_gqtzdb.log 
Mon Jul 03 18:19:10 2017 Using STANDBY_ARCHIVE_DEST parameter default value as /oradata/gqtzdb/archivelog ALTER SYSTEM SET log_archive_dest_state_2='ENABLE' SCOPE=BOTH; Mon Jul 03 18:19:10 2017 PING[ARC2]: Heartbeat failed to connect to standby 'gqtzdb_dg'. Error is 16047.

　　接着查看v$archive_dest視圖，查看是否能找到原因，結果發現如下報錯：

SQL> select dest_id,error from v$archive_dest;

   DEST_ID ERROR
---------- -----------------------------------------------------------------
         1
         2 ORA-16047: DGID mismatch between destination setting and target database

　　很明顯，DGID不一樣，去備庫查看參數db_unique_name參數：

SQL> show parameter db_unique_name

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
db_unique_name                       string      gqtzdb

　　發現db_unique_name參數沒有修改，仍然是主庫的值，速度改過來，並重啟備庫：

SQL> alter system set db_unique_name='gqtzdb_dg' scope=both;
alter system set db_unique_name='gqtzdb_dg' scope=both
                 *
ERROR at line 1:
ORA-02095: specified initialization parameter cannot be modified


SQL> alter system set db_unique_name='gqtzdb_dg' scope=spfile;

System altered.

　　然后再在主庫開啟歸檔路徑2，在備庫運行命令，查看同步狀態：

SQL> alter database recover managed standby database using current logfile disconnect from session;

Database altered. SQL> select process,client_process,sequence#,status from v$managed_standby; PROCESS CLIENT_P SEQUENCE# STATUS --------- -------- ---------- ------------ ARCH ARCH 0 CONNECTED ARCH ARCH 0 CONNECTED ARCH ARCH 0 CONNECTED ARCH ARCH 0 CONNECTED RFS UNKNOWN 0 IDLE RFS LGWR 24 IDLE RFS UNKNOWN 0 IDLE RFS UNKNOWN 0 IDLE MRP0 N/A 11 APPLYING_LOG 9 rows selected.