ORA-12516 TNS Listener cannot find an available handler that meets the protocol stack requirements

A database on the server appears ' Ora-12516:tns: The listener cannot find an available process that meets the protocol stack requirements ' error, to resolve the problem first look at the number of existing processes in the database, whether the parameter processes has reached the size.

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A. select COUNT (*) from v$process; Gets the current number of processes in the database.
B. select value from v$parameter where name = ' processes '; gets the upper limit of the number of processes.
1, view the current number of sessions, processes and sessions values, found that the value of the session number and 2 parameters are very close to 2, modify the processes and sessions values sql> alter system set processes=300 Scope=spfile;
The system has changed.
Sql> alter system set sessions=335 Scope=spfile;
The system has changed. 3. View the processes and sessions parameters, but the changes do not take effect 4. Restart the database for the changes to take effect

ORA-12516 TNS Listener cannot find an available handler that meets the protocol stack requirements