Medline etc ...

Larry Hunter hunter at work.nlm.nih.gov
Wed Jun 10 14:21:33 EST 1992

Paul Gilna writes:

   ... look at the evidence we are facing today; the available servers are
   processing literally 1000's of queries per day, and this rate is climbing
   with no sign of abating, GenBank is already placing load limiters on the
   retrieval queues... Together, these factors dramatically increase the
   significance of the consequences of a system failure (or even planned
   downtime) to a community becoming increasingly dependant on a centralised
   data distribution mechanism--cd-roms may be slow, but you're going to get
   er, annoyed, when you cannot get your ...  results back because you are
   behind 500 other jobs and you are three time zones away.

   And I'll bet that's only a glimmer of what would happen if the entire
   Medline user community could suddenly dial or internet in to NLM!

But (almost) the entire Medline user community *can and does* dial in to NLM!
The two main access methods to Medline are by ELHILL and Grateful Med, both of
which work by dial in or via telnet (the commercial service, not internet).
Although it requires two large mainframes and a large disk array to make it
work, it supports many hundred simultaneous users.  When I log in, I typically
see more than 150 people online, and I believe the system processes on the
order of 10 million queries a day.  Yet access is fast enough to be
interactive.  Furthermore, all kinds of precautions are taken to ensure the
integrity and availability of the system, so down time is rare.  Read-only
database access is relatively easy to scale up to handle arbitrarily large
numbers of users, given sufficient resources.  (Think about directory
assistance operators or airline reservation systems.)

This is not to say that centralized data sources are the only reasonable
alternative.  NLM has also sold licenses to institutions that want to run their
own local versions, as well as to commercial entities who produce value-added
CD-ROMs that offer, e.g., different user interfaces or search engines.

As noted, NCBI also produces and distributes the Entrez CD-ROM, which provides
a sequence-related subset of Medline, as well as Genbank, SwissProt, PIR and
the NCBI Backbine, all with a unified, multiplatform interface and a search
engine capable of functioning in multiple dataspaces simultaneously.

NLM is investigating a variety of further alternatives for providing access to
this and other information relevant to biomedical researchers, clinicians and
others.  Although I am not aware of any specific plans, I know their have been
experiments exploring the challenges of making Medline available over the

Please don't innundate me with requests for more details.  I'm a basic
researcher in Machine Learning at NLM's Lister Hill Center, and have no
official association with either Medline or NCBI.  For information about NLM
generally and Medline specifically, call the Medlars Management Section at
(800) 638-8480 within the US, or +1 301 496 6193 outside the US.  For
information about the NCBI CD-ROM, call +1 301 496 2475 or send email to
info at ncbi.nlm.nih.gov.


Lawrence Hunter, PhD.
National Library of Medicine
Bldg. 38A, MS-54
Bethesda. MD 20894
(301) 496-9300
(301) 496-0673 (fax)
hunter at nlm.nih.gov (internet)

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