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From: dlw@odi.com (Dan Weinreb)
Newsgroups: comp.databases
Subject: Re: OODMS-RDBMS Wars (Was: Extended RDB vs OODB)
Message-ID: <1989Aug28.213958.1292@odi.com>
Date: 28 Aug 89 21:39:58 GMT
References: <3560052@wdl1.UUCP> <408@odi.ODI.COM> <3324@rtech.rtech.com> <1037@unify.UUCP> <161@servio.UUCP>
Reply-To: dlw@odi.com
Organization: Object Design, Inc.
Lines: 28
In-reply-to: penneyj@servio.UUCP's message of 21 Aug 89 16:34:09 GMT

In article <161@servio.UUCP> penneyj@servio.UUCP (D. Jason Penney) writes:

I agree with almost everything you say, but I'd like to comment on one
paragraph.

   Arguments about in-memory caching are spurious (as others have pointed
   out), because all successful databases must reduce disk accesses to
   a minimum and rely on primary memory caching to achieve adequate performance.

Not everything that has been said in comp.databases about memory
caching is spurious.  It is true that a relational database could
follow the same caching protocols as any object-oriented database, in
principle.  However, in commercial practice, the distributed
relational database systems use certain kinds of caching and
distribution that are very different from the kind of thing that we
are using.  Neither kind of caching is "right" or "wrong"; each is
appropriate for certain kinds of usage patterns, and for certain
applications.  Neither is tied in a theoretical sense to any
particular data model, but they might be *correlated* to some degree
with data model, and other attributes of a DBMS, based on the target
market for the DBMS product.  Certainly all DBMS's will strive to
minimize disk access, and certainly all will use some form of primary
memory caching to do it, but the next level of detail differs from one
DBMS to another and can have large effects on performance.  The paper
by Rubenstein, Kubliar, and Cattell that was recently cited in
comp.databases goes into this question in greater detail.

Dan Weinreb		Object Design, Inc.		dlw@odi.com