"string" stands either for the connection name that is resolved with the Oracle "tnsnames.ora" file which should be located in your ORACLE_HOME(Oracle install dir)\NETWORK\ADMIN directory or for a connection string like this one :
connection_name = the name you want for this connection, eg : "CON1"
ip_address = the ip address of the machine on which the Oracle instance is running
listener_port = the port on which the Oracle listener is listening, the default value is 1521.
listener_service_name = the name of the service corresponding to the instance you want to connect to. If you don't know it, then issue "lsnrctl status" on the machine running the instance and you will see which services are managed by the listener.
HTH & Regards,
ORA-000TK : No bind variable detected... Shared Pool Alert code 5 - Nuclear query ready .