TNS-12541: TNS:no listener

lins

## Question

```shell
TNS-12541: TNS:no listener
TNS-12560: TNS:protocol adapter error
  TNS-00511: No listener
   Linux Error: 111: Connection refused
```



## Resolve

- 切换用户  

  ```shell
  [root@dbserver ~]# su - oracle
  [oracle@dbserver ~]$

  ```



- 切换环境变量  `

  ```shell
  [oracle@dbserver ~]$ . oraenv
  ORACLE_SID = [orcl] ? orcl
  The Oracle base remains unchanged with value /u01/app/oracle

  ```



- 登录数据库   

  ```shell
  [oracle@dbserver ~]$ sqlplus / as sysdba                  
  SQL*Plus: Release 19.0.0.0.0 - Production on Wed Dec
  Version 19.21.0.0.0

  Copyright (c) 1982, 2022, Oracle.  All rights reserved.


  Connected to:
  Oracle Database 19c Standard Edition 2 Release 19.0.0.0.0 - Production
  Version 19.21.0.0.0

  ```



- 显示服务名  

  ```shell
  SYS@orcl >show parameter service_names;

  NAME                                 TYPE        VALUE
  ------------------------------------ ----------- ------------------------------
  service_names                        string      orcl

  ```



- 强制注册服务

  ```shell
  SYS@orcl >alter system register;

  System altered.

  ```



- 查看监听状态

  ```shell
  [oracle@dbserver ~]$ lsnrctl status listener

  LSNRCTL for Linux: Version 19.0.0.0.0 - Production on

  Copyright (c) 1991, 2023, Oracle.  All rights reserved.

  Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=dbserver)(PORT=1521)))
  STATUS of the LISTENER
  ------------------------
  Alias                     LISTENER
  Version                   TNSLSNR for Linux: Version 19.0.0.0.0 - Production
  Start Date               
  Uptime                    0 days 0 hr. 50 min. 42 sec
  Trace Level               off
  Security                  ON: Local OS Authentication
  SNMP                      OFF
  Listener Parameter File   /u01/app/oracle/product/19.21/db_1/network/admin/listener.ora
  Listener Log File         /u01/app/oracle/diag/tnslsnr/dbserver/listener/alert/log.xml
  Listening Endpoints Summary...
    (DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=dbserver)(PORT=1521)))
    (DESCRIPTION=(ADDRESS=(PROTOCOL=ipc)(KEY=EXTPROC1521)))
  Services Summary...
  Service "0c4b59438c6b17f3e0637885a8c04522" has 1 instance(s).
    Instance "orcl", status READY, has 1 handler(s) for this service...
  Service "86b637b62fdf7a65e053f706e80a27ca" has 1 instance(s).
    Instance "orcl", status READY, has 1 handler(s) for this service...
  Service "orcl" has 1 instance(s).
    Instance "orcl", status READY, has 1 handler(s) for this service...
  Service "orclXDB" has 1 instance(s).
    Instance "orcl", status READY, has 1 handler(s) for this service...
  Service "pdb" has 1 instance(s).
    Instance "orcl", status READY, has 1 handler(s) for this service...
  The command completed successfully

  ```


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