LNNVL is a SQL function that takes a condition as an argument. It returns TRUE if the condition is FALSE or NULL. It returns FALSE if the condition is TRUE. It is available but not documented in Oracle database versions prior to 10gR1.
SQL> select * from dual where not lnnvl(1=1); select * from dual where not lnnvl(1=1) * ERROR at line 1: ORA-03113: end-of-file on communication channel SQL> select * from dual; ERROR: ORA-03114: not connected to ORACLE
It looks like a bug to me.