Constraint stats ORA-02298

Alter table CEXIST DISABLE constraint CEXISTBROKBOOK;

alter table CEXIST disable constraint CEXISTBOOK;
alter table CEXIST ENABLE constraint CK_COMPANYCATEGORY
alter table CEXIST ENABLE constraint CEXISTPRIMARY ;
alter table CEXIST ENABLE constraint COMPANYEXIST ;




SQL> alter table CEXIST ENABLE constraint CEXISTBOOK ;
alter table CEXIST ENABLE constraint CEXISTBOOK
*
ERROR at line 1:
ORA-02298: cannot validate (LDBO.CEXISTBOOK) - parent keys not found


alter table CEXIST MODIFY CONSTRAINTS CEXISTBOOK ENABLE VALIDATE;

ERROR at line 1:
ORA-02298: cannot validate (LDBO.CEXISTBOOK) - parent keys not found



alter table CEXIST MODIFY CONSTRAINTS CEXISTBOOK ENABLE NOVALIDATE;



Constraint stats
Here are the four type of constraint stats. These four constraint stats are applicable for all type of constraints(primary key, foreign key, check etc).

1. ENABLE VALIDATE
2. ENABLE NOVALIDATE
3. DISABLE VALIDATE
4. DISABLE NOVALIDATE


ENABLE VALIDATE is same as ENABLE. Constraint validate the data as soon as we entered in the table.


ENABLE NOVALIDATE is not same as ENABLE. Constraint validates the new data or modified data. It would not validate the existing data in table.


DISABLE NOVALIDATE is the same as DISABLE. The constraint is not checked so data may violate the constraint.


DISABLE VALIDATE means the constraint is not checked but disallows any modification of the constrained columns.



Note : Couple of things needs to be noted down here.

1. Converting NOVALIDATE constraint to VALIDATE would take longer time, depends on how big the data in the table. Although conversion in the other direction is not an issue

2. Disabling primary key constraint will drop the index associated with primary key. Again, when we enable the primary key constraint, it will create the index on the primary key column.

What is the ideal place to use ENABLE NOVALIDATE option?

In a busy environment, some one disabled the constraint accidently or intentionally, and we have already bad data in that table. Now business requested you to load the new set of data, but business wanted to make sure that new set of data should be validated during the load. At this circumstances, we can use ENABLE NOVALIDATE option. This option will validate the new data and old data will not be validated.

What is the ideal place to use DISABLE VALIDATE option?

We disabled the constraint for some reason. We do not want to load any data until we fix the issue and enable the constraint. We can use DISABLE VALIDATE option here. This option would not let you load any data when the constraint is disabled.