Yes. There are many on different platforms (and they vary by platform).
I don't know specifically for your's, but on many implementations, the
key/data pair must fit entirely into an internal block which is usually
only a few thousand bytes in size (if that). I believe that some
implementations require that all keys that resolve to the same hash must
all fit in the same block.
This seriously (and almost randomly) limits the usefulness of ndbm as
a slapd backend except for the most trivial of databases.
Craig
Innosoft