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

You try to connect with Oracle database and get Ora-12518 listener could not hand off client connection error.

Now what action is to be taken to get rid of above error? Follow below steps to resolve the issue.

Connect with oracle database:

C:\>sqlplus / as sysdba

SQL>conn testuser/test@mydb

And you got the ERROR: ORA-12518: TNS: listener could not hand off client connection

Solution-1:

First check your database whether it is in start mode or not.

SQL> shutdown immediate;

SQL> Startup;

Solution-2: If first is not working 

You have to increase PROCESSES initialization parameter in Oracle database.

First use the following command to check the existing value of the PROCESSES.

show parameter processes

As we have already started our database normally or using spfile, then run following command to alter system processes to 450.

alter system set processes=450 scope=spfile;

If you have started your database using pfile, process parameter must be set in pfile.

Solution-3: If both the above solutions are not working.

If you are getting ORA-12518 because of a shared server issue then you first need to use the below command to shutdown the dispatcher.

SQL> alter system shutdown immediate 'D001';

Then add on new dispatchers.

SQL> alter system set DISPATCHERS = '(protocol=tcp)(dispatchers=3)';

Resolving ORA-12518 requires you to evaluate the syntax depending on your dispatcher value in the Spfile.ora or init.ora files.  When you increase DISPATCERS to resolve ORA-12518 you should also keep an eye on the shared server ratio.

Resolved ORA-12541: TNS no listener error

ORA-28001: The Password Has Expired

I hope you have successfully resolved your Ora-12518 issue.