Oracle Database Discussions

Hello all,
Can someone give me detailed explanation on RELY constraint.
What I have with me is as below:
The ETL process commonly verifies that certain constraints are true. For example, it
can validate all of the foreign keys in the data coming into the fact table. This means
that you can trust it to provide clean data, instead of implementing constraints in
the data warehouse. You create a RELY constraint as follows:
ALTER TABLE sales ADD CONSTRAINT sales_time_fk
FOREIGN KEY (sales_time_id) REFERENCES time (time_id)
RELY DISABLE NOVALIDATE;
RELY constraints, even though they are not used for data validation, can:
=> Enable more sophisticated query rewrites for materialized views.
=> Enable other data warehousing tools to retrieve information regarding
constraints directly from the Oracle data dictionary.

Creating a RELY constraint is inexpensive and does not impose any overhead
during DML or load. Because the constraint is not being validated, no data
processing is necessary to create it.



I need more and detailed information on this constraint.
It will be a great help for me.
Thanks in advance.
Himanshu