Let’s start the series of Oracle listener. Now are going to focus over the issue for the following errors. Let’s have looked over the steps and solve the issues.

TNS-12516 TNS: listener could not find an instance with the matching protocol stack
ORA-12516 TNS: listener could not find available handler with the matching protocol stack
TNS-12519 TNS: no appropriate service handler found
ORA-12519 TNS: no appropriate service handler found
ORA-12520 TNS: listener could not find available handler for requested type of server


None of the known and available service handlers for the given SERVICE_NAME support the client’s protocol stack: transport, session, and presentation protocols.


check if the number of current connections by using the following command in Unix:

ps -ef | grep oracleSID | grep -v grep | wc –l

Check process parameter in the database

SQL> select * from v$version;



Oracle Database 11g Enterprise Edition Release – 64bit Production

PL/SQL Release – Production

CORE Production

TNS for Linux: Version – Production

NLSRTL Version – Production
SQL> show parameter processes

——————--- ———–--- --——-
processes integer 200

SQL> select count(*) from v$process;




Increase process:


session=(1.5 * PROCESSES) + 22

SQL> alter system set processes=300 scope=spfile;

Processes is not a dynamic parameter, so you need to restart the database to take the effect.

Thought of the Day!

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