Thursday, February 10, 2011

what is ELDM (Extended Logical Data Modeling) ?

ELDM is very important in terdata data modeling. It comes after Logical modeling
and before physical modeling of database.

1. ELDM is very important and needs extra care. otherwise wrong inputs will go Physical modeling
2.The ELDM will become our final input into the Physical Data Model.
3. In developing Any teradata Physical database, we go through
Logical Design
ELDM
Physical Design
4.The Logical Data Model will be the input to the Extended Logical Data Model.
The Extended Logical Data Model will be input to the Physical Data Model.

5.demographics of data is very important. which we get by questioning logical data modelers

6. Logical data Modeling:
The LDM is a logical representation of tables that reside in the data warehouse database
Once the tables are defined, related, and normalized, the Logical Data Model is complete. Teradata recommends third normal form tables. we can also limit to 2NF

The completed Logical Data Model is used as a basis for the development of the Extended Logical Data Model (EDLM).

7.The ELDM includes information regarding physical column access and data demographics for each table. This also serves as input to the implementation of the Physical Data Model. The ELDM contains demographic information about data distribution, sizing, and access.

The two major components of an ELDM are the following:

COLUMN ACCESS in the WHERE Clause or JOIN CLAUSE.

DATA DEMOGRAPHICS.

8.Physical Database Design portion where we choose our Primary Indexes and Secondary Indexes.

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