SQL> conn sys/sys@pr:1521/pr10 as sysdba
Connected.
SQL> conn sys/sys@pr:1521 as sysdba
ERROR:
ORA-12514: TNS:listener does not currently know of service requested in connect
descriptor


Warning: You are no longer connected to ORACLE.
SQL> conn sys/sys@pr:1521/pr10 as sysdba
Connected.
SQL> sho parameter service

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
service_names                        string      pr10
SQL> alter system set service_names = 'pr' ;

System altered.

SQL> sho parameter service

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
service_names                        string      pr
SQL> conn sys/sys@pr:1521 as sysdba
Connected.