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151 - ORA-12541 TNS no listener

An ORA-12541 error occurs when the listener for the destination server is down or unreachable.
This can be due to the listener not being started or being incorrectly configured, or it can be due to a network connection problem.

Two likely reasons for the error:

  • The database was briefly unavailable at the time when you tried to access.
  • The Oracle client application on your machine is not configured correctly.

        See: "ORA-12154 TNS could not resolve connect identifier specified", Oracle error message

if your listener has been started correctly, and got "ORA-12541 TNS no listener" error.

To solve the ptoblem :

1. Run SQL*Plus and login as SYSDBA.

# sqlplus / as sysdba

2. Check the number of process

SQL> select machine, program, count(*) from v$session where username != 'SYS' group by machine, program

If it exceeds the maximum processes, you need to increase the value.

SQL> show parameters processes

  NAME                                 TYPE        VALUE
  ------------------------------ ----------- -------------
  aq_tm_processes                integer     1
  db_writer_processes            integer      2
  gcs_server_processes          integer     0
  global_txn_processes          integer     1
  job_queue_processes          integer     2
  log_archive_max_processes  integer     4
  processes                           integer    100

3. Run the command “alter system set processes=1500 scope=spfile;” in the SQL*Plus

SQL> alter system set processes=1500 scope=spfile;

4. Restart Database



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