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Question about Buffer Access Time

Following sentences is description of Buffer Access Time of Dialog response time in ST03.

Buffer Access Time

Certainly, buffer access requires some time in the u03BCs/ms range, depending on the amount of requested data and the type of access. This time is not reported separately. Effectively, buffer access time is knocked down to processing time. In extreme cases, buffer accesses can even take seconds! Why is that? Data is buffered with a structure according to its primary index; the buffer does never contain indexes. Thus, accessing the buffered data other than by primary index may result in high buffer access time.

My questions are:

1. How to understand "Data is buffered with a structure according to its primary index"? When a table is fully buffered, all records are buffered. What else will be buffered?

2. If a table has a large data volume and it's fully buffered into memory, when application wants to query from the buffered table, what's the execution plan, only full table scan in memory?

Please advise. Thanks

James

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1 Answer

  • Dec 04, 2008 at 02:53 PM

    1. How to understand "Data is buffered with a structure according to its primary index"? When a table is fully buffered, all records are buffered. What else will be buffered?

    Nothing else.... just data

    2. If a table has a large data volume and it's fully buffered into memory, when application wants to query from the buffered table, what's the execution plan, only full table scan in memory?

    No... it looks at the index and the index send them to the buffered data.

    Regards

    Juan

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