ETL Prototype using Oracle Warehouse Builder - Part 3
August 28, 2003
In the previous articles, we gained a basic understanding of Oracle Warehouse builder architecture and became familiar with its various components. My previous articles on Oracle Streams implementation etc., simply served as pointers towards standard implementation scenarios for the developer community. However, here, before we go ahead with building an ETL prototype, I would like to share my views on choosing the Oracle Warehouse Builder as a tool in an Oracle data warehouse life cycle management project and my experience (the "pain" or ease of using it) in building this prototype.
Common concerns of choosing an ETL tool
Very often, we notice, the common concerns that have been raised by project managers and other decision makers in a Data warehouse life cycle project is whether a "tool" is good enough to achieve the desired results in relatively less time than the traditional way of coding and maintaining the data warehouse objects. Also raised are issues such as advantages of warehouse builder over the other innumerable vendor tools that are available in the market today. Most importantly, in choosing a good team, the interviewer's tend to focus on whether the developer/ candidate has a good "knowledge" of the tool itself with very less or no importance to the basic concepts of the designing, developing and maintaining a data warehouse life cycle.
Building a prototype using Oracle Warehouse Builder will address most of the above concerns with the emphasis that one of the requirements would be that the candidate have a clear understanding of building and maintaining a data warehouse. The focus should also be on the developer's faculty in at least one programming language such as UNIX shell script and PL/SQL, Java, (for an Oracle based data warehouse) C etc. more than the tool itself.
As we already know, Oracle Warehouse Builder (OWB - as the name suggests) is a tool that can be effectively used in a complete Oracle based data warehouse life cycle development and maintenance environment and can very well integrate with other Oracle tools such as Oracle Portal, Oracle Discoverer and Oracle Workflow, for implementing or achieving pertinent business functionality.
Among the many phases, ETL is one of the most important phases and most often, an "ETL" tool is evaluated and chosen to implement this phase of the data warehouse life cycle. Again, we can have disparate source for loading data into a target warehouse schema and thus the ETL processes can range from being very basic in nature to very complex designs. In addition, loading data into the target warehouse schema can involve varied classes of transformations, the most commonly used being pre-written and provided as "transformation" libraries by vendors and others that require custom programming are developed by the warehouse developers.
Choosing Oracle Warehouse Builder
Some of the pros and cons of using the Oracle Warehouse Builder over traditional data warehouse development and management are (extensible to other tools too):
1. All the stages and processes can be designed, planned and implemented systematically and actual "coding" (for most part it may not involve coding at all) can be come later during implementation. The graphic editors will give a complete picture of the how the components (source modules, mappings, transformations, targets, etc.) are involved/interact in the system and the associated process flows.
2. Component management. - It is very important to keep track of all the components that go into the data warehouse--the source modules, objects, the mapping objects, the various transformations, the targets, processes and the real time status.
3. Change management - A single change in the requirement can be implemented with relative ease as compared to implementing in a "home-grown" approach. Such changes can also be efficiently tracked (audit) and recorded for later analysis.
4. Most transformations are readily available and do not have to be written from scratch, thereby saving a lot of valuable time and resources. This time and resources can be devoted to other tasks that demand attention such as performance management etc.
5. Visibility - Visibility is very important in the transformation process as to what the processes are achieving.
6. Standards - Unlike the "home grown" approach, design, development and implementation standards can be effectively enforced.
7. Deliverables - A data warehouse project, is never a "do-doing-done" scenario, but among other things involves a continuous changing scenario (during the development phase and in most cases in the "maintenance" phases too), data and performance management (load tuning etc.) and interfacing with other systems. However, most often the development team has to produce quick deliverables and maintain the least possible time window in change management or implementations. In addition, Oracle Warehouse Builder does effectively facilitate such tasks and considerably reduces the deliverables time window.
1. The initial stage in installing and configuring Oracle Warehouse Builder can be a little cumbersome due to the various versions, compatibility, patches and "bug-fixes" but this is offset by the many other advantages listed above.
2. One of the biggest advantages of using homegrown over vendor provided ETL tools is that as a root level developer, it has been very easy to get-in and "tweak-and fix" any code as per the business requirement. However working with any ETL tool requires one to turn to the product support team for "fixes" in most cases (well, developers do get work arounds but the fact remains). Thus, there is a trade-off over such flexibility. However, one thing to note about Oracle Warehouse Builder is, since all of its transformations are written in PL/SQL, it is easy to "customize" the code to suit our requirements and even get-into the transformation and debugging if required. In addition, Oracle now provides the Java API /SDK to programmatically manipulate the metadata such as performing batch operations on the meta-data without having to use their Java client tools.
In a homegrown environment, it is only the development code/objects and plain old editors we tend to use (usually the preferred choice) and no Java clients etc., which require additional resources. Again, this is relatively trivial, and offset by the many advantages presented by Oracle Warehouse Builder and due to the availability of resources. However, in some cases it pays to use custom code rather than use any tool fabricated code due to performance and managibility reasons. Feel free to share post suggestions or comments or share your experiences in the Oracle Warehouse Builder group.