ORA-12514: TNS:listener does not currently know of service requested in connect descriptor

ORA- Error:

SQL*Plus: Release 18.0.0.0.0 - Production on Tue Jun 9 00:10:02 2020 Version 18.3.0.0.0

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SQL> ERROR:

ORA-12514: TNS:listener does not currently know of service requested in connect descriptor

SQL> 

SP2-0640: Not connected

SP2-0641: "EXECUTE" requires connection to server

SQL>

Cause:

Running Stored Procedure or Active session got terminated with ORA-12514: TNS:listener does not currently know of service requested in connect descriptor , listener has refused the connection considering PMON process of database declined the request which hints issue in database accepting new connection such as below ..

Database issue can be anything like db is mount stage , corruption , archivelog full , process resource limit exceeded etc.

ORA-12514 received at client server due to process exceed ORA-00020 on DB

ORA-00020: maximum number of processes (750) exceeded

ORA-20 errors will not be written to the alert log for

the next minute. Please look at trace files to see all

the ORA-20 errors.

Process P367 submission failed with error = 20

.

.

Process P367 submission failed with error = 20

TABLE SYS.WRI$_OPTSTAT_HISTHEAD_HISTORY: ADDED INTERVAL PARTITION SYS_P31904 (1794) VALUES LESS THAN (TO_DATE(' 2020-06-09 08:50:31', 'SYYYY-MM-DD HH24:MI:SS', 'NLS_CALENDAR=GREGORIAN'))

TABLE SYS.WRI$_OPTSTAT_HISTGRM_HISTORY: ADDED INTERVAL PARTITION SYS_P31907 (1794) VALUES LESS THAN (TO_DATE(' 2020-06-09 08:50:40', 'SYYYY-MM-DD HH24:MI:SS', 'NLS_CALENDAR=GREGORIAN'))

Process P367 submission failed with error = 20

.

.

 

Solution:

Increase process limit at database instance ..

alter system set process=1000 sid='*' scope=spfile;

In other cases , verify db alert as a starting point to troubleshoot error ORA-12514 ; as in most of the cases tnsping would be working fine.