What is De-normalization?

De-normalization is the process of attempting to optimize the performance of a database by adding
redundant data. It is sometimes necessary because current DBMSs implement the relational model
poorly. A true relational DBMS would allow for a fully normalized database at the logical level, while
providing physical storage of data that is tuned for high performance. De-normalization is a technique
to move from higher to lower normal forms of database modeling in order to speed up database access.