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Message Posted: Sun, 29 Aug 1999 @ 16:40:18 GMT


     
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Subj:   Re: How to stop or avoid Rollback or recovery process
 
From:   Eric J. Kohut

Assuming that you are specifically concerned about update processes.

Here are two additions to these comments from John.

First, many updates can be turned into the insert / select approach that John mentions especially when combined With the mult- statement requests. You can change an update into a insert that changes the column value with a case statement or with a where clause That identifies the rows to change and then combine this with a second request to insert / select the rows that don't Qualify in the first.

Second, V2 R3 greatly reduces the need to worry about the time required to journal the rows in an update operation and therefore the time to roll back such operations. This improvement becomes more efficient as the # of targeted update rows, as compared to the entire table, becomes larger.


If are talking about a greater variety of operations. Here are few approaches.

* Then you should try to avoid ANSI mode with required explicit transactions and therefore commits.

* Try to minimize long forced transactions caused by ANSI mode or with Begin / End transactions in Teradata Mode.

* Also you can insert the rows targeted for update operations into a second table so that your update can be a join based on the primary index values needed for the update process. This can often a good approach for a small # of targeted update rows as compared to the entire table.

* Try to combine multiple simple steps which use update operations into more complex anded operations in a single select or a single update Operation when the logic allows option. Often this is possible when using a case statement.

* Finally rethinking you current SQL logic by taking entirely different approaches.


Finally, Teradata allows some very complex operations and as a result it can require some additional thought to completely take full advantage of its Power, but the new V2R3 performance improvements make simpler operations much more efficient.


EJK
Eric J. Kohut
Senior Solutions Consultant - Retail Solutions Group
NCR Corp.



     
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