Increasing performance when sequentially reading an indexed file



A customer has noticed that on a rather large indexed file, the performance seems to suffer when reading sequential through the entire file.

Is there a way to increase the performance of indexed file I-O when doing sequential reads?


They might look into using the extfh.cfg option called NODESIZE.
This controls the size of the index nodes that are used for a file when it is created.

The larger the value, the more keys that can be stored into a single node and this can speed up sequential processing quite a bit.

In a recent test when reading sequentially through an indexed file containing 8 million records, the following timings were achieved by setting the NODESIZE and recreating the file:

NODESIZE     Timing
1024                3 mins 55 secs
4096                3 mins 03 secs
16384              1 mins 59 secs



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