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Message Posted: Tue, 13 Aug 2013 @ 12:52:00 GMT

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Subj:   Re: Space occupied in varchar columns
From:   Dieter Noeth

Yep, two things :-)

#1: the available diskspace on a datablock is less than 512 bytes, there'a a datablock header of (afaik) 72 bytes:

     512 - 72 = 440 bytes available

#2: every row has a row header, which is at least 14 bytes (depending on Presence/Compress Bits/PPI).

The first variable column in a table needs 4 bytes overhead and each addtitional VarChar 2 bytes.

Plus a NULL still needs some space unless it's COMPRESSed (i never checked the sizing rules for a compressed VarChar)


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