Oracle database listening file configuration

Check the listening status ：

[[email protected] ~]$ ps -ef | grep tns
root       336     2  0 11 month 24 ?      00:00:00 [netns]
oracle    4978  4540  0 14:17 pts/2    00:00:00 grep --color=auto tns
oracle   28540     1  0 12 month 04 ?      00:00:01 /u01/app/oracle/product/12.1.0/db_1/bin/tnslsnr LISTENER -inherit
[[email protected] ~]$ lsnrctl status LISTENER

LSNRCTL for Linux: Version 12.1.0.2.0 - Production on 05-DEC-2021 14:17:35

Copyright (c) 1991, 2014, Oracle.  All rights reserved.

Connecting to (ADDRESS=(PROTOCOL=tcp)(HOST=172.20.3.20)(PORT=1521))
STATUS of the LISTENER
------------------------
Alias                     LISTENER
Version                   TNSLSNR for Linux: Version 12.1.0.2.0 - Production
Start Date                04-DEC-2021 14:30:43
Uptime                    0 days 23 hr. 46 min. 52 sec
Trace Level               off
Security                  ON: Local OS Authentication
SNMP                      OFF
Listener Parameter File   /u01/app/oracle/product/12.1.0/db_1/network/admin/listener.ora
Listener Log File         /u01/app/oracle/diag/tnslsnr/ydhl/listener/alert/log.xml
Listening Endpoints Summary...
  (DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=172.20.3.20)(PORT=1521)))
Services Summary...
Service "RZCDB" has 1 instance(s).
  Instance "cdb", status READY, has 1 handler(s) for this service...
Service "cdb" has 1 instance(s).
  Instance "cdb", status UNKNOWN, has 1 handler(s) for this service...
The command completed successfully

View listening file configuration

[[email protected] ~]$ cat /u01/app/oracle/product/12.1.0/db_1/network/admin/listener.ora
LISTENER =
  (ADDRESS_LIST=
        (ADDRESS=(PROTOCOL=tcp)(HOST=172.20.3.20)(PORT=1521))
  )
SID_LIST_LISTENER=
   (SID_LIST=
        (SID_DESC=
          (GLOBAL_DBNAME=cdb)
          (SID_NAME=cdb)
          (ORACLE_HOME=/u01/app/oracle/product/12.1.0/db_1)
        )
    )