Performance and Capacity of Centralized and Distributed Online Catalogs: Part 1 — Centralized Online Catalogs
| Date | 01 March 1986 |
| DOI | https://doi.org/10.1108/eb047652 |
| Pages | 7-23 |
| Published date | 01 March 1986 |
| Author | Hank Epstein |
| Subject Matter | Information & knowledge management,Library & information science |
Performance and Capacity of Centralized
and Distributed Online Catalogs:
Part
1
- - Centralized Online Catalogs
Hank Epstein
The design of an
online public access catalog
greatly affects the performance
and capacity requirements
of the computer system.
The characteristics of
traditional menu and
command-driven systems
that most affect performance
are explained.
There are many papers, presentations, chapters,
and books which describe the functions of an online
catalog. Functions describe "what" the system
does:
for example, permit the user to search by
any author's last name, or any word in the title
or subject.
In this paper, I will discuss a different aspect
of online catalogs: the issue of performance and
capacity. Performance describes "how fast" the
functions are performed, or "how many" functions
can be performed in one hour. Capacity describes
the maximum levels that can actually be supported
by the software and the hardware. Performance
and capacity are highly interrelated, and are at
least as critical as the functions of an online catalog,
especially for an online catalog used by patrons.
Online catalogs are particularly vulnerable to ex-
ceeding the performance and capacity limits of
the system.
Once the online catalog system is installed
and operating, it will generally receive increasingly
heavy use as patrons become more familiar with
it. As additional terminals are added to meet the
patrons' needs, the response time increases. As
the file grows because of new titles cataloged or
retrospective conversion, the response time also
increases. As a result of the increase in the size
of the file and the simultaneous increase in the
use of terminals, the response time could increase
dramatically: from a few seconds to a few minutes,
and in some recent cases to fifteen and thirty min-
utes.
By the time the highly visible response time
has increased beyond acceptable limits (as perceived
by the patrons), it may be too late for the library
to do anything about the situation without the
Epstein is one of the technical pioneers of
online library systems, having been the director
of BALLOTS (now the RLIN network of the Re-
search Libraries Group). He has developed the
MITINET/retro and MITINET/marc systems for the
Apple and IBM PC microcomputers, which provide
retrospective conversion and full MARC-record
cataloging support to small libraries. His firm,
Information Transform of Madison, Wisconsin, pro-
vides support to libraries implementing automated
systems, with emphasis on technical systems eval-
uation, procurement, acceptance testing, and imple-
mentation. This paper is a revised version of
"Performance and Capacity of Online Catalogs:
Measuring Response Time with a Stopwatch Verses
an Hourglass" which was originally published in
Online Catalogs/Online Reference: Converging
Trends (Chicago, IL: American Library Association,
1984).
Copyright © 1986 by Hank Epstein.
ISSUE 15 7
substantial unplanned costs of upgrading to a
larger system or acquiring a new system. Unfor-
tunately, this sequence of events has already oc-
curred in some libraries, and is likely to occur
more frequently in the near future.
Some libraries with online catalogs
no longer permit patrons to perform
Boolean searching because of the resul-
tant system degradation.
Some libraries with online catalogs no longer
permit patrons to perform Boolean searching be-
cause of the resultant system degradation. The
patrons in these libraries are therefore denied the
use of the very feature that makes online catalogs
powerful and effective. Ironically, the "availabil-
ity" of Boolean searching may have influenced the
library in selecting the particular system. In these
cases,
the Boolean function is part of the system,
yet it cannot be utilized because of performance
limitations.
The purpose of this paper is to assist library
staff members in planning for an adequate online
catalog operation in their institutions. Selecting
an adequate online system primarily involves avoid-
ing an inadequate system. This may sound simple
or self-evident, but the task of determining
whether a system is adequate is extremely complex.
This paper emphasizes "traditional" mainframe
systems and database structures which form the
basis of most current integrated library systems.
BRIEF DESCRIPTION OF AN ONLINE CATALOG
The ultimate tool for finding library materials
is an interactive, online patron access catalog.
Such catalogs permit library staff members and
patrons to use computer terminals, microcomputers,
or dial-up terminals in their local libraries to ver-
ify the existence and determine the location of
desired materials. An online catalog eliminates
the need for a card, book, or COM catalog, except
for emergency backup purposes. Few commercially
available online catalogs with the functions and
performance characteristics described in this paper
are fully operational at present, nor are fully op-
erational systems likely to be in widespread use
over the next three years.
An online catalog should contain full biblio-
graphic records that can be used as a source of
cataloging information for the staff or bibliograph-
ic verification for the patron. Linked with each
bibliographic record that represents a book, film,
phonograph record, or other item should be an
indication of each branch or library that owns
the material, the local call number, volume number,
copy number, and location. Each patron should
be able to search the online catalog file by any
of a variety of access points, including authors,
individual words in the title and/or subject headings,
the call number, the Library of Congress card num-
ber, the ISBN, and any other useful access points.
For those records selected as the result of
the user's search, the user should be able to review
full or partial bibliographic information, a list of
libraries or branches owning the item, and the
local library information about the item. This should
be the case with both local and shared regional
catalogs. With an online local library catalog, only
the holdings of the individual library should be
included in the database; therefore only local holdings
information would be available for display to the
staff or patron.
GENERAL REQUIREMENTS OF AN
ONLINE CATALOG
For an online catalog to replace the current
card, book, or COM catalog, several conditions
should be met.
1.
The quality of bibliographic data in the online
catalog should be equal to or better than that of
the data in the original catalog.
2.
The number of access points in the online
catalog should be equal to, and preferably greater
than, the original catalog. At minimum, the online
catalog should list the title, any authors, and subject
headings. Added access points could include subject
and title keywords, keyword access for corporate
and conference authors, the call number (with trunca-
tion or call number ranges), series, the Library
of Congress number, the ISBN, the publication date,
local and special subject terms, cross-references,
language, country of publication, type of material,
reading level/intended audience, form of reproduc-
tions (microfilm, large print) and a variety of other
access points available from full MARC records.
3.
The form of access to the bibliographic records
should utilize some type of interactive searching,
providing the user with intermediate results at
each step in the search. This allows the user to
react to the results and influence the next step
in the search. The user should be able to back
up one or two steps in the search, and be able
to continue on a different search path, without
having to start from the beginning.
4.
The system should provide more than one
level of user interface to accommodate users with
varying levels of sophistication and expertise.
For instance, a menu system might be quite adequate
8 LIBRARY HI TECH
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