Observation Length, Alignment, and Padding for a SAS Data Set
There are three different cases for alignment.
•Observations within a SAS data set are aligned on double-byte boundaries whenever
possible. As a result, 8-byte and 4-byte numeric variables are positioned at 8-byte
boundaries at the front of the data set and followed by character variables in the
order in which they are encountered. If the data set only contains 4-byte numeric
data, the alignment is based on 4-byte boundaries. Since numeric doubles can be
operated upon directly rather than being moved and aligned before doing
comparisons or increments, the boundaries cause better performance. ...
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