Description
This function resynchronizes the internals of the sditerator to
the data on disk. The default locking mode does that automatically
and so this normally will not need to be used. Some locking modes
do not do that. In that case, another process (e.g. an on-line
filler) can write to the data on disk. In that case, the sditerator
will not see those changes until this function is called.
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