单实例下实例监听日志
[oracle@dbserver ~]$ more /u01/app/oracle/diag/tnslsnr/dbserver/listener/trace/listener.log

WARNING: Subscription for node down event still pending
20-JUL-2022 21:50:17 * (CONNECT_DATA=(CID=(PROGRAM=)(HOST=dbserver)(USER=oracle))(COMMAND=status)(ARGUMENTS=64)(SERVICE=LIST
ENER)(VERSION=186647552)) * status * 0
WARNING: Subscription for node down event still pending
20-JUL-2022 21:50:18 * (CONNECT_DATA=(CID=(PROGRAM=)(HOST=dbserver)(USER=oracle))(COMMAND=status)(ARGUMENTS=64)(SERVICE=LIST
ENER)(VERSION=186647552)) * status *'WARNING Subscription for node down event still pending' in Listener Log

单实例的数据库环境，建议进行如下操作：
[oracle@dbserver ~]$ echo $ORACLE_HOME
/u01/app/oracle/product/11.2.0/db_1
[oracle@dbserver ~]$
[oracle@dbserver ~]$ cd $ORACLE_HOME
[oracle@dbserver db_1]$ pwd
/u01/app/oracle/product/11.2.0/db_1
[oracle@dbserver db_1]$
[oracle@dbserver db_1]$ cd network/admin/
[oracle@dbserver admin]$ pwd
/u01/app/oracle/product/11.2.0/db_1/network/admin
[oracle@dbserver admin]$ ls
listener.ora  samples  shrept.lst  sqlnet.ora  tnsnames.ora
[oracle@dbserver admin]$

[oracle@dbserver admin]$ vim listener.ora
添加：
SUBSCRIBE_FOR_NODE_DOWN_EVENT_<listener_name>=OFF
如下：
[oracle@dbserver admin]$ more listener.ora
# 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 = dbserver)(PORT = 1521))
      (ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1521))
    )
  )

ADR_BASE_LISTENER = /u01/app/oracle
SUBSCRIBE_FOR_NODE_DOWN_EVENT_LISTENER=OFF
[oracle@dbserver admin]$

[oracle@dbserver admin]$ lsnrctl reload