1) Find the violate constraint rows in your Oracle DB.

As we known, "enable validate", "enable" for new values, "validate" for old values to make constraints work. If you Oracle DB default option is enable and novalidate, then you want to modify to enable and validate so that make all data confirm some constraints . Unfortunatly, may you find some data real violate constraints, however, you could not find where it is. So following method could help you. It is not a big deal, I just write it down to a shell script. 1@@@@ Here, I write a shell scirpt to make it work     [oracle@station78 ~]$ cat ./check_violate_constraint_rows.sh     #!/bin/sh     #please intput $1 table_name, $2 constraint_name     read -p "Please input table name (like hr.employees): " tab     read -p "Please input constraint name(like chk_xxx):  " cons     sqlplus / as sysdba<< EOF > violate_constraint_rows.txt     DROP TABLE exceptions PURGE;     @\$ORACLE_HOME/rdbms/admin/utlexpt1.sql     ALTER TABLE $tab ENABLE VALIDATE CONSTRAINT $cons EXCEPTIONS INTO EXCEPTIONS;     SELECT * FROM $tab WHERE ROWID IN (SELECT row_id FROM exceptions);     EOF     echo " "     echo "You could check the output file violate_constraint_rows.txt !!! "     echo "Find the violate constraint rows, and do something."     echo " " @@@Usage Example   [oracle@station78 ~]$ ./check_violate_constraint_rows.sh   Please input table name (like hr.employees): test.t_trainsupport_executions   Please input constraint name(like chk_xxx):  CHK_TRAINSUPPORT_EXEC_CUSTFAC      You could check the output file violate_constraint_rows.txt !!!   Find the violate constraint rows, and do something.      [oracle@station78 ~]$ cat violate_constraint_rows.txt   SQL*Plus: Release 10.2.0.1.0 - Production on Mon Dec 31 15:15:05 2012   Copyright (c) 1982, 2005, Oracle.  All rights reserved.   Connected to:   Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - 64bit Production   With the Partitioning, OLAP and Data Mining options   SYS@ocm>   Table dropped.     SYS@ocm>   Table created.     SYS@ocm>   Table altered.     SYS@ocm>   no rows selected     SYS@ocm> Disconnected from Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - 64bit Production   With the Partitioning, OLAP and Data Mining options 2@@@@ Here I write a sql script to make it work. SYS@ocm> !cat x.sql     DROP TABLE exceptions PURGE;     @\$ORACLE_HOME/rdbms/admin/utlexpt1.sql     ALTER TABLE &&table_name     ENABLE VALIDATE CONSTRAINT &constraint_name     EXCEPTIONS INTO EXCEPTIONS;     SELECT * FROM &table_name WHERE ROWID IN (SELECT row_id FROM exceptions); @@@Usage Example:   SYS@ocm> @x.sql   Table dropped.   Table created.     Enter value for table_name: test.t_trainsupport_executions   old   1: ALTER TABLE &&table_name   new   1: ALTER TABLE test.t_trainsupport_executions   Enter value for constraint_name: CHK_TRAINSUPPORT_EXEC_CUSTFAC   old   2: ENABLE VALIDATE CONSTRAINT &constraint_name   new   2: ENABLE VALIDATE CONSTRAINT CHK_TRAINSUPPORT_EXEC_CUSTFAC     Table altered.     old   1: SELECT * FROM &table_name WHERE ROWID IN (SELECT row_id FROM exceptions)   new   1: SELECT * FROM test.t_trainsupport_executions WHERE ROWID IN (SELECT row_id FROM exceptions)     no rows selected