OBIEE Logical Table vs Logical Table Sources – Best Practice

The difference between Logical Tables, Logical Table Sources (LTS) and the physical tables that compose a Logical Table Source, here are some basic guidelines that have helped me get this concept to seat more clearly in my mind.

businesmodellayer-logical-table LT LTS

BMM Layer - Logical Table and LTS

Logical Tables like organization in the picture on the left are used to create drill down paths or dimensions like Dim_Organizaition.

Usually when you drag and drop a column from a table that is not currently being used in your logical table, the physical table containing such column gets added as a new Logical Table Source (LTS) such as UofA on the image on your left. This most usually is not the result you should be aiming for, in general, when a the column you are adding to a Logical Table comes from the same system of record you have been using you should just rename the LTS to reflect the name of the system of record in the same fashion we renamed ours to UofA and then go edit the sources for this LTS.

The confusion often stems from having what I would call “Logical Table Source” Sources (LTSS). The image below depicts them for UofA, you can acces this dialog by double clicking any LTS.

BMM - Logical Table Source Properties and LTSS

BMM - Logical Table Source Properties and LTSS

Physical Table FRS_GL_ACCOUNTS is a “Logica Table Source”  Source (LTSS) for Logical Table Source UofA. The rationale again is that UofA represents a system of record (source) that brings in information from more than one physical table to build our organization logical table.

If you still have questions add comments to this post and let’s get the discussion started 🙂

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2 responses to “OBIEE Logical Table vs Logical Table Sources – Best Practice

  1. Hi Ignacio,

    Thanks for braving the subject of Logical Table Sources and putting this out there! 🙂 I have been playing with OBIEE for some time now, and I must admit, the nuances between having multiple Logical Table Sources in a Logical Table versus multiple “Logical Table Source” Sources (LTSS) as you put it, is a pretty confusing notion.

    So far, the only times I’ve seen the reason to create multiple Logical Table Sources in the “Sources” folder of a Logical Table is when we have a Logical Column that references separate, partitioned physical data source information (for example, customers “A-M” in Table1 and customers “N-Z” in Table2) or when we have a Logical Column that could reference aggregated fact information as well as finer-grain detail fact information in different physical sources (“Amount Sold” coming from an aggregated fact table, and “Amount Sold” coming from the sales detail fact table). In either case, you have to go to the “Content” tab for EACH corresponding Logical Table Source to specify the fragmentation content formula and check the box for multiple sources (in the case of the “A-M”, “N-Z” example) or specify the Dimension/Logical Level hierarchy information (in the case of the aggregation example).

    All my other experiences, I have used the regular “create one Logical Table Source and update it with more than one ‘Logical Table Source’ Sources (LTSS)”, as you defined the term. It sounds like to me that this is the approach that we more often than not want to take, correct?

    Does that make sense to you Ignacio? If so, am I using both approaches to Logical Table Sources correctly?

    Many thanks,

    Jeremy

    • Hey different levels of aggregation are a good was a very good example of the use of Logical Table Sources, as Jeremy mentions you have to explicitly declare the level of aggregation on the content table of each of the different Logical Table Sources.

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