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  3. July 2004

RE: Variable length fields

VARLEN(0) will give the best space usage, as everything is packed into the auxiliary space. This is reflected in the results given. If most of the data is shorter than the allocated length, there will be wasted space. The overhead to link the records to the auxiliary space can have a bearing. Just as in ZIP files, there are instances where the "compressed" version is larger than the original.

The drawback to VARLEN(0) is performance - up to double the I/O to get the records. If you are lucky and the auxiliary space has data for multiple varlen columns fairly close together, so that the pages are already in memory for the next record, it won't be too bad. But it's a crapshoot.

Vern

At 11:40 AM 7/1/2004, you wrote: 
David,

Did you by any chance reverse the figures for cases 1 and 2?  It makes no
sense that the file is larger for the allocated length case _unless_ a
substantial number of the fields had content that exceeded the allocated
length.  Perhaps that was the case in your tests.

As has been noted earlier, VARLEN will only save storage when a substantial
proportion of the records have content _within_ the allocated length.

Jon Paris
Partner400
www.Partner400.com

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