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

You may get below error when trying to connect to the database using sqlplus or through an application login.

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

Reason:

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

Solution;

 Increase PROCESSES initialization parameter.

Use the following command to check the value of the PROCESSES initialization parameter:

show parameter processes;

If the database was started using an spfile, then the following command can be used to increase the PROCESSES initialization parameter:

alter system set processes=600 scope=spfile;

If the database was started using a pfile, then the value of the processes parameter must be changed in the pfile and the database bounced.