搭建dg启动物理备库到nomount状态后，测试连通性时发现备库能正常连接主库，但主库却没法连接备库，报错ora-12528

问题描述：搭建dg启动物理备库到nomount状态后，测试连通性时发现备库能正常连接主库，但主库却没法连接备库，报错ora-12528，如下所示.
主库：主机名 risdb + oracle 11.2.0.4
备库：主机名 risnewdg + oracle 11.2.0.4
1、问题重现

2、问题排查
--查备库监听文件
# listener.ora Network Configuration File: /u01/app/oracle/product/11.2.0/db_1/network/admin/listener.ora
# Generated by Oracle configuration tools.

LISTENER =
  (DESCRIPTION_LIST =
    (DESCRIPTION =
      (ADDRESS = (PROTOCOL = TCP)(HOST = simnewdg)(PORT = 1521))
      (ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1521))
    )
  )

ADR_BASE_LISTENER = /u01/app/oracle

SID_LIST_LISTENER =
   (SID_LIST =
     (SID_DESC =      
       (GLOBAL_DBNAME = simnewdg)                   
       (ORACLE_HOME = /u01/app/oracle/product/11.2.0/db_1)                  
       (SID_NAME = simnewdg)                                               
     )
)
--查备库tnsnames.ora文件
[oracle@simnewdg admin]$ cat tnsnames.ora 
risdb =
  (DESCRIPTION =
    (ADDRESS = (PROTOCOL = TCP)(HOST = risdb)(PORT = 1521))
    (CONNECT_DATA =
      (SERVER = DEDICATED)
      (SERVICE_NAME = simdb1)
    )
  )

SIMNEWDG =
  (DESCRIPTION =
    (ADDRESS = (PROTOCOL = TCP)(HOST = simnewdg)(PORT = 1521))
    (CONNECT_DATA =
      (SERVER = DEDICATED)
      (SERVICE_NAME = simdb1)
    )
  )
--查备库数据库信息
SQL> show parameter name

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
cell_offloadgroup_name               string
db_file_name_convert                 string       /u01/app/oracle/oradata/spectr
                                                            a/datafile/, /data/risdb/, /u0
                                                           1/app/oracle/oradata/spectra/t
                                                            empfile/, /data/risdb/
db_name                                 string         spectra
db_unique_name                       string         simnewdg
global_names                         boolean         FALSE
instance_name                          string         simnewdg
lock_name_space                       string
log_file_name_convert                string        /u01/app/oracle/oradata/spectr
                                                             a/logfile/, /data/risdb/
processor_group_name                 string
service_names                            string      simdb1

解决方案：
a、修改监听文件中global_dbname=simdb1
或者
b、修改tnsname.ora 中的 simdb1 的服务名 service_name=simnewdg