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Message Posted: Wed, 20 Jul 2000 @ 01:19:54 GMT


     
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Subj:   Re: Oracle vs Teradata DBA maintenance
 
From:   John K. Wight

See my $.02 worth below.

JK John K. Wight Senior Solutions Consultant - Teradata Solutions Group NCR Corp.

  -----Original Message-----
From: Timothy Gist
Sent: Wednesday, July 19, 2000 12:26 PM
Subject: Re: Oracle vs Teradata DBA maintenance
 


  I am not an Oracle or Teradata DBA, however, I worked in an environment where we utilized Oracle as our Production DB and Teradata as our Warehouse DB. I was jointly responsible for the maintenance of our system which involved in minor Oracle and Teradata Maintenance and the over-all performance of the system. Without knowing specific questions regarding maintenance, I will say that Oracle seems to require more overhead than Teradata and is certainly less forgiving than Oracle.  


[JK Wight] Less forgiving is probably another way of saying Teradata does more foe me in terms of checking, parsing, etc. due to a much more mature cost base optimizer. Oracle requires more DBA/SQL Codes support because the optimizer is not a 'smart' as the Teradata optimizer. e.g. if I have a 5 table join in a query (considered small to medium type query) Oracle is sensitive to the ordinal position of the tables in the FROM clause and the size of the table. If you re-arrange them into a different order you will get a different time to execute - or in some cases, it may never come back! (Just experience). Hence you have a lot more 'tuning' with Oracle. Teradata's Optimizer is not sensitive to this and you can put the tables in any order! This is important if you are using query tools to generate your SQL!!!!!!!


  Oracle also seems to require more re-orgs than normal.  


[JK Wight] Teradata never requires re-orgs - PERIOD! That means either tables or indexes. Teradata is the only RDBMS that applies relational principles of no order - either rows or columns (E. Codd is on record in article on this).


  Now this could be related to the Database structure, but we purchased a Sun 6500 and moved our Oracle DB to the new machine which would be a Reorg. Performance improved dramatically as expected, [JK Wight] Of course because there was an initial reorg to load the data to the new system (??). however, in less than a year later, Database retrieval was beginning to slow down to a noticeable level yet our environment would not dictate such a performance drop-off in the short amount of time. The conclusion (last of I knew of) was Reorg. Reorgs in Oracle are very time consuming. [JK Wight] They are very time consuming in Oracle, DB2, SQL Server, Informix, etc. etc.  


  One more thing: If you run the same query against the same table with the same layout in Teradata and Oracle, the results would be very different: Teradata would take about 1/10 of the time than Oracle does to retrieve the data.  


[JK Wight] Again, being a parallel processing engine (i.e. Teradata) it does everything in parallel. In a DSS environment (i.e. data warehouse) this is extremely important when processing large volumes of data with complex and un-predicable queries - i.e. ad-hoc.


Hope this helps.



     
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