How to modify the setting of concurrent connections in Oracle

The Oracle database cannot be connected, and related errors are prompted.

OERR: ORA-12519 TNS: no appropriate service handler found
Client Connection intermittent failure, error ORA-12519

Cause: the listener cocould not find any available service handlers that are

Appropriate for the client connection.

Action: run "lsnrctl services" to ensure that the instance (s) have registered

With the listener, and are accepting connections. Check the lsnrctl service and the instance has been registered,

When the status shows ready, you can connect.

When the listener believes the current number of connections has reached maximum load,

It may set the state of the service handler for an instance to "blocked" and begin refusing

Incoming client connections with either of the following errors: ora-12519 or ora-12516

Using dynamic service registration, PMON obtains the current connection status through SERVICE_UPDATE, but SERVICE_UPDATE has a time interval,

Therefore, the number of connections displayed by listener may be different from the current number of connections.

Query solution:

Check whether the number of existing processes in the database has reached the processes parameter size.

1. select count (*) from v $ process; obtain the current number of processes in the database.

2. select value from v $ parameter where name = 'processs'; obtain the maximum number of processes.

3. If the upper limit is reached, modify the processes size in initSID. ora.

4. Restart the database to the nomount state, execute create spfile from pfile, and start up open.

Queries the maximum number of concurrent queries since the database is started.

Modify the maximum number of connections:
Alter system set processses = 300 scope = spfile;

Restart the database:
Shutdown immediate;
Startup;

-- View which users are currently using data
SELECT osuser, a. username, cpu_time/executions/1000000 |'s ', SQL _fulltext, machine
From v $ session a, v $ sqlarea B
Where a. SQL _address = B. address order by cpu_time/executions desc;

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