oracle : any version
Users usually connect to oracle database,
but, today, they get the following error :
ORA-12514, TNS:listener does not currently know of service requested in connect descriptor
You need to find the unsuccessful connection entries in the listener.log :
TNS-12516: TNS:listener could not find available handler with matching protocol stack
If you find the TNS-12516 error, you have to increase the value
of the processes and sessions parameter
in pfile or spfile and then restart your database.