Partitions and Fragments

Partitions and Fragments:

1.What is Fragmentation and where it is used?

A) The fragmentation (known also as partitioning) is the most powerful feature of OBIEE. You can fragment (or partition) any logical table (fact table as dimension table) in more than one logical table source (LTS).For the same logical table, you may have more than one logical table source (or physical table as one logical table source is always mapped to only one physical table).

2. What are the Types of  Partitioning  and Fragmentation?

A) You have three sort of fragmentation:

a. Fact-based / Dimension-based fragmentation.

b. Content-based / Value-based fragmentation.

c. Level-based fragmentation / aggregate navigation.

3. What is Fragment and Fragmented Data?

A) A fragment is a logical table source that does not contain the entire set of data at a given level.

a.The type data that the fragment does contain must be set.

b. Fragmented data is data from a single domain that is split between multiple tables (multiple fragments).

4. What is Fact-Based Vertical Partitioning/Fragmentation?

A) This technique allow you to :

a. mix two facts table with two different grains (the level based partitioning).

1.perform a densification (to preserve dimension value) : OBIEE - Densification with the fact-based fragmentation capabilities.

2.partition vertically your fact table.

3.federated the query of two different data sources : OBIEE - Federated Query with Excel Sheet.

It's also known as :

a. Fact-based partitioning.

b. Fact partitioning outer join.

c. Fact-based fragmentation.

You implement it by creating in the Business Model Layer:

a. one logical fact table with two logical tables source for the same level of content.

B.Two logical fact tables joined with the same logical dimension (known as conforming Dimensions).

c. When minimum one measure of each logical fact table are included in the query, the BI Server generates two queries for each logical table source and perform a full outer join between them by the dimension columns.

5. What are the Rules to Configuration Value-based Fragmentation?

A) The same set of columns must be mapped for each fragment.

a. If a logical table is sourced from a set of fragments, it is not required that every individual      fragment maps the same set of columns.

b. If all the fragments of a logical table map the same set of columns, than the set of fragmented sources is considered to be the whole universe of logical table sources for the logical table. This means that measure aggregations can be calculated based on the set of fragments.

c. If the set of mapped columns differ across the fragments, than the Oracle BI Server assumes that it does not have the whole universe of fragments, and therefore it would be incorrect to calculate aggregate rollups (since some fragments are missing). In this case, the server returns NULL as measure aggregates.

The whole domain must be defined

a. A domain can have many sources. The sources have to all follow the rule that each level must contain sources that, when combined, comprise the whole domain of values at that level.

6. What is the Principle for Aggregate Navigation with level-based fragmentation?

A) Each logical dimension table will have multiple table sources at each level of granularity and a hierarchy which specifies the unique keys for each level. The central FACTS table will also have all of the logical fact sources from each level of aggregation and these sources will need to have the grain of each fact source declared as well.