ORA-12518: TNS: listener could not hand off client connection on my database.


The error occurred during the application connectivity. Suddenly application starts throwing the following error and starts droping the new connection.

ORA-12518: TNS: listener could not hand off client connection on my database.

Application Error: ODBC Error 12518: [Oracle][ODBC][Ora]ORA-12518: TNS:listener could not hand off client connection


  1. Check the resources usage limit in Oracle
select RESOURCE_NAME,CURRENT_UTILIZATION,MAX_UTILIZATION,LIMIT_VALUE from v$resource_limit where resource_name in ('sessions','processes');

2. Current utilization reached the limit value of the resources. Then we need to increase the process parameters in Oracle and restart the database to make changes effects.

--- check the processes allocated to DB
SQL> show parameter processes;  

--- Double the  increase the count of processes
SQL> alter system set processes=800 scope=spfile;

3. Restart the Database to make changes in effects:

Shutdown immediate;

Note: Check which module causing lot of application process or sessions:

-- Check the no of processes
SELECT s.program,s.machine,count(p.spid) from v$session s,v$process p where 
s.paddr = p.addr group by s.program,s.machine having count(p.spid) > 5;

--Check the no of sessions
SELECT s.program,s.machine,count(*) from v$session s group by s.program,s.machine;

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