SQL & PL/SQL

I am using the utl_match function jaro_winkler_similarity on a table in a Oracle 10g database installation in order to find possible duplicates.
In short, the sql statement is:
select
p1.id, p1.codi, p2.id, p2.codi
from
empreses p1, empreses p2
where
p1.id<>p2.id
and
utl_match.jaro_winkler_similarity(p1.codi,p2.codi)>=90;

There are 10000 tuples in this table which definition is:
describe empreses;
Name Null? Type
----------------------------------------- -------- ----------------------------
RELEVANCIA FLOAT(126)
ID NOT NULL NUMBER
DATA_ALTA DATE
CODI VARCHAR2(200)

The query ALWAYS ends with an error:
ERROR:
ORA-03113: end-of-file on communication channel

How could I trace this error? Is there any other function effectively enough to search duplicates?