java.sql.SQLException: Listener refused the connection with the following error: ORA-12519, TNS:no appropriate service handler found

Question

I am passing Resultset object to each thread. Each thread is connecting to the database and inserting data. Untill thread 110 it is working fine. After it crosses 111 thread it

Answer 1

Your multi-threaded application is opening too many Connections/Sessions. Hence, the listener is dropping and blocking new connections for a while.

Check your DB resource usage first:

SELECT * FROM v$resource_limit WHERE resource_name IN ('processes','sessions');

Check to see if your MAX_UTILIZATION for either your Processes or Sessions is getting too close to the LIMIT_VALUE. If yes, you should either:

1. Use DB Connection pooling to share Connection objects between threads. Or,
2. Increase the number of processes/sessions that Oracle can service simultaneously.

Actually, Connection Pooling (#1) should always be done. An application cannot scale up otherwise. Check Apache Commons DBCP for details. For #2, open a new SQL*Plus session as SYSTEM and run:

ALTER system SET processes= scope=spfile;

to increase backend concurrency. Then RESTART the Database. IMPORTANT!