Detection and correction of constraint violations

You can avoid problems by running CHECK DATA with DELETE NO to detect violations before you attempt to correct the errors.

If required, use DELETE YES after you analyze the output and understand the errors.

You can automatically delete rows that violate referential or table check constraints by specifying CHECK DATA with DELETE YES. However, you should be aware of the following possible problems:

The violation might be created by a non-referential integrity error. For example, the indexes on a table might be inconsistent with the data in a table.
Deleting a row might cause a cascade of secondary deletes in dependent tables. The cascade of deletes might be especially inconvenient within referential integrity cycles.
The error might be in the parent table.

CHECK DATA uses the primary key index and all indexes that exactly match a foreign key. Therefore, before running CHECK DATA, ensure that the indexes are consistent with the data by using the CHECK INDEX utility.