Data, data en nog eens data

Category: data warehousing

  • Requirements analysis

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    tom
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    Recently I read a very interesting book on requirements analysis “Mastering the Requirements Process: Getting Requirements Right” by Suzanne Robertson and James Robertson. They wrote a practical book that lead to a template for such a document They advocate to spend enough time on requirements analysis, which can be described shortly as “getting to know…

  • Context diagrammes – understanding a scope

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    tom
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    I came accross a very nice technique that can be used to show the scope of a project. It is called the Context Diagramme. The idea is that the system is shown as one item. The internal structure within the system is not displayed. Instead the diagramme shows the interaction from the system with external…

  • Yet another checklist

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    tom
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    I often come across checklists. Such checklists are used to assess the quality of, say, a database. See here for an example of such a checklist. In this case, we have a checklist that is created to assess the quality of a Teradata database. Such checklist are very interesting. They are generally based on a…

  • MOLAP and ROLAP

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    tom
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    I currently work in an organisation that has a debate on whether to use MOLAP or ROLAP. But first of all: what is discussed here? ROLAP and MOLAP are two different techniques to store data that are meant for OLAP analysis. In ROLAP the data are stored in tables in a relational database and each…

  • The Teradata answer on materialised views

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    tom
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    Teradata has a feature that is designed to increase the performance of queries. This feature is called the “join index”. Such a join index is a structure that stores the outcomes from a query. These outcomes are stored permanently and they wait for the moment when they are called. The syntax of such a join…

  • Soft RI in Teradata

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    tom
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    Teradata has the concept of “Soft RI”. In this concept, a foreign key is created but its restriction is not enforced. What happens in that situation? Let’s look at the normal situation of referential integrity. Suppose, we have two tables. One table is referred to by a second table. If a foreign key is created,…

  • Running scripts in teradata

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    tom
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    Let us assume, we have a data warehouse in teradata. Let us suppose that this data warehouse is loaded with a set of scripts. In principle it could be done. The question then arises how the scripts are run. An example could clarify this. The example looks like: .logon oTDD001.s2.ms.****.com/TOM.VAN-MAANEN, pau26688 .export report file=C:\Users\TOM.VAN-MAANEN\phi.txt .set…

  • Security and compliance

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    tom
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    Security and compliance has many different aspects. In the list below, I try to provide an overview on these aspects. We have seen: Authentication. Is the person really the person that he says he is. Principal Propagation. If someone from system A issues a command that system B will start, system B will need to…

  • A check list for the assessment of a data warehouse

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    tom
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      Yet another checklist Regularly, one comes across an assignment whereby one has to assess a data warehouse. (at least in my type of work). I found a nice checklist that allows a quick overview on a data warehouse. It is composed of several sections, each one covering a certain area. Going through this list,…

  • Skeleton Functional Design

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    tom
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    Quite often, I have to write a functional design. Such a design can be a tedious job. Part of time is spent is spent on how to represent the findings. One would like to present a nice / concise report. The writing process itself is made easier if a template is available. To this end,…