Hi,

Sometimes You can get “ORA-12518: TNS:listener could not hand off client connection  ” error.

ORA-12518 TNS listener could not hand off client connection

Details of error are as follows.

ORA-12518: TNS:listener could not hand off client connection

Cause: The process of handing off a client connection to another process failed.

Action: Turn on listener tracing and re-execute the operation. Verify that the listener and database

instance are properly configured for direct handoff. If problem persists, call Oracle Support.

Or This error may be related with out of available Oracle processes parameter.

If processes parameters are insufficient, then you should increase the PROCESSES parameter as follows.

SQL> show parameter processes

NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
aq_tm_processes integer 1
db_writer_processes integer 1
gcs_server_processes integer 0
global_txn_processes integer 1
job_queue_processes integer 1000
log_archive_max_processes integer 4
processes integer 1500
SQL>
SQL>
SQL> alter system set processes=2000 scope=spfile;

System altered.

SQL>

Restart database after this operation.

If it is not related with processes parameter, then it may be related with dispatcher.

Firstly Shutdown the dispatcher and add new dispatchers as follows.

SQL> show parameter dispatchers
SQL> select name from v$dispatcher;
SQL> alter system shutdown immediate 'D001';
Add new dispatcher
SQL> alter system set DISPATCHERS = '(protocol=tcp)(dispatchers=4)';

Or you should check ‘max user processes’ etc. with ‘ulimit -a‘ command, and if it is insufficient, then increase it.

For windows environment.

set logging_listener_name=on in the listener.ora and reload the listener.

Or restart all Oracle services, it will be fine.

Do you want to learn more details about RMAN, then read the following articles.