In theory, incremental hotcopy of a Berkeley DB repository can be done by
squirreling away a base hotcopy (datafiles + logfiles), and then incrementally
copying only (but *all* of) the Berkeley DB logfiles thereafter. The logfiles
are designed to be such that they can be replayed in sequence to enact their
changes to the BDB datafiles. So incremental hotcopy N+1 might copy the BDB
logfiles which are newer than those captured in hotcopy N, then replay those
logfile actions into the backed-up datafiles.
Unfortunately, the default behavior of 'svnadmin create' is to configure BDB to
automatically remove its unused logfiles (those whose actions have already been
reflected in the datafiles). One would need to disable that auto-purging
functionality for such an approach to incremental hotcopy to be viable.