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Message Posted: Wed, 03 Aug 2005 @ 11:34:44 GMT

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Anony Wrote:

There are several gotcha's that I have seen migrating from Oracle to Teradata. It is vital to understand both Oracle/Teradata technologies.

Teradata loves what Oracle hates. What does this mean? Teradata can handle things like correlated subqueries, large volume data sets and parallel processing. It was designed for the data warehousing space and not the Online Transactional Process arena.

When migrating from Oracle to Teradata take some extra thought on your Primary Indexes. The primary index is the most important piece of the pie for performance. The PI will define how your data will be laid out across the AMPs. This is vital...

Make sure your design supports both the ETL process and the User Queries. What I have seen happen more often than not is the ETL team uses the PI has the Primary Key. This means the ETL team focuses on using Unique Primary Indices (UPI) in the table design to load into the warehouse. This is good for the ETL side but not very thought out for the User side. Remember, the ultimate goal is not to load the data, but to retrieve the data.

Stored procedures in Teradata are not as sophisticated as stored procedures in Oracle. Why is this??? Using stored procedures in Teradata oftentimes limits the parallel processing that is the center point of Teradata's ability to perform. When using cursors the processing goes to sequential processing so you may wish to consider your use of stored procedures in the Teradata system.

On the ETL side of the fence... We use Informatica along with the Teradata Utilities. There are features in both that compliment one another. Informatica will support the Teradata load utilities and is a self-documenting tool. It takes a little longer to build the ETL processes in Informatica but you do have an audit trail of data mappings and processes that you can use for monitoring and metrics reporting.

Data types are not a big deal. Dates will need to be transformed of course but once you determine the translation of data types from Oracle to Teradata it is repeatable and is not a huge learning curve.

This of course is only my 2 cents.

Chris Coffing Air Force Knowledge Services (AFKS) Lead Operations & Support Lead Teradata DBA Teradata NCR Contractor Teradata Certified Master

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