Connect to Oracle DB using SQLPLus without a tnsnames.ora

Run ....

sqlplus  /nolog

This will place you in the SQL prompt without logging on.

From here you can run the conn command

For example...

SQL> conn clarkeb@'(DESCRIPTION_LIST=(LOAD_BALANCE=off)(FAILOVER=on)(DESCRIPTION=(CONNECT_TIMEOUT=5)(TRANSPORT_CONNECT_TIMEOUT=3)
RETRY_COUNT=3)(ADDRESS_LIST=(ADDRESS=(PROTOCOL=TCP)(HOST=jupiter1)(PORT=1621)))(CONNECT_DATA=(SERVICE_NAME=BPM_DB)))(DESCRIPTION=(CONNECT_TIMEOUT=5)(TRANSPORT_CONNECT_TIMEOUT=3)(RETRY_COUNT=3)(ADDRESS_LIST=(ADDRESS=(PROTOCOL=TCP)(HOST=jupiter2)(PORT=1621)))(CONNECT_DATA=(SERVICE_NAME=BPM_DB))))'