plogan@apd.mentorg.com (Patrick Logan) (06/07/91)
It is not entirely clear what is being described below. Rather than
propose my interpretation, I am looking for other opinions and
experiences.
From "UNIX Today!", May 13, 1991, pp. 58, 64...
[Paraphrasing: Dan Gerson, Xerox PARC, is developing collaborative
systems, in particular a document database that will allow
multiple users and track versions. He's not sure OODBs are best
for his work. He's using a Sybase DBMS and is investigating
ObjectStore from Object Design.]
[Quoting: typing errors are mine.]
But OODBMSes have their drawbacks as well. "Currently, OODBMSes
are not very well developed," he [Gerson] says.
"The basic problem in an OODBMS is in the user I/O inside of a
transaction," Gerson adds. "Programs in an RDBMS have a looser
connection to the data. Users issue an SQL query, the data base
gets a table, makes a copy of it, and the user looks at it on his
screen."
During a transaction in an OODBMS, objects are loaded into memory,
either real or virtual. "As soon as you execute a transaction, you
can't see the object anymore," he says. "In an RDBMS, the system
is giving you some sort of a copy. In an OODBMS, the system is
giving you the actual object, so they're only valid in a
transaction."
Gerson syas he believes few people are aware of this fundamental
flaw in OODBMS technology because so few systems are out there.
Those that are function as single-user, workstation-based
development systems, not multiuser systems where deadlocks can
occur. Besides, he says, he thinks some OODBMS vendors are either
unaware of the possible problem or deliberately ignoreing it.
[End of quote.]
--
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