or like this :-
DELETE FROM abc WHERE (a,b) IN ( SELECT a,b FROM abc t2, ( SELECT SUM(z),x,y FROM xyz GROUP BY x,y ) test WHERE t2.a = test.x AND t2.b = test.y )
DELETE FROM abc WHERE (a,b) IN ( SELECT x,y FROM xyz )
ORA-03113 end-of-file on communication channel Cause: An unexpected end-of-file was processed on the communication channel. The problem could not be handled by the Net8 two-task software. This message could occur if the shadow two-task process associated with a Net8 connect has terminated abnormally, or if there is a physical failure of the interprocess communication vehicle, that is, the network or server machine went down. In addition, this message could occur when any of the following statements/commands have been issued: ALTER SYSTEM KILL SESSION ... IMMEDIATE ALTER SYSTEM DISCONNECT SESSION ... IMMEDIATE SHUTDOWN ABORT/IMMEDIATE/TRANSACTIONAL Action: If this message occurs during a connection attempt, check the setup files for the appropriate Net8 driver and confirm Net8 software is correctly installed on the server. If the message occurs after a connection is well established, and the error is not due to a physical failure, check if a trace file was generated on the server at failure time. Existence of a trace file may suggest an Oracle internal error that requires the assistance of Oracle Support Services.