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Archives of the TeradataForum
Message Posted: Fri, 23 Sep 2005 @ 12:48:18 GMT
| Subj: | | Re: Executing queries in parallel |
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| From: | | Victor Sokovin |
| | In term of SQL multi statement request are executed by using ";", I am not able to understand What is exactly meant by parallel
execution? | |
| | The answer from my end is open multiple sessions and execute the query's. | |
MSR have a few advantages. For example, SQL statements run as MSR form one transaction. This is often used when you have to insert data from
multiple sources into an empty table. In case of failure the rollback is easy so TD does not need to journal MSR inserts on a detailed level. This
means a big performance boost compared to a series of sequential inserts into the same table. Not to mention the advantages of transactional
management: you get either everything or nothing. Also, if the statements are not super-heavy, running them in parallel just means using the
resources of the system more efficiently. The run time of an MSR would very often be smaller than the sum of run times of the sequentially
submitted statements.
The only thing I don't like about MSR is their incredibly awkward syntax which relies on exact text formatting. As it happens, the layout is
often destroyed when it needs to go via third party tools or the hands of users who are not aware of the MSR subtleties.
Regards,
Victor
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