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Archives of the TeradataForum
Message Posted: Sat, 30 Nov 2002 @ 16:49:24 GMT
| Subj: | | Re: Oracle vs Teradata compare |
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| From: | | Judge, James A |
Couple of thoughts. Assuming the Teradata schema to hold the Oracle schema is the same. If so, and you have most of your Oracle columns
defined as VARCHAR2 you should try to convert the columns to CHAR where appropriate in Teradata. This data discovery will allow you to
determine any COMPRESS values for columns. IF there are the usual number of default values in the CHAR columns, as well as dates, and
numeric then you can get significant dasd savings in Teradata. With minimal COMPRESS usage conservatively, I would say 15%; but the last
two migration efforts I have been involved with have yielded 30-35% reduction in row size due to more extensive evaluation and use of
COMPRESS.
As far as indexing overhead it depends on expected access paths of the data; although as you have probably seen in previous posts
Teradata usage of secondary indexes is more "particular" than Oracle. If you have an index in Oracle for ordering then you will tend to not
have it in Teradata. But, those are general statements and need to be evaluated on your part.
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