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From: jbn@glacier.STANFORD.EDU (John B. Nagle)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Mainframes vs micros for database applications
Message-ID: <13905@glacier.STANFORD.EDU>
Date: Sat, 3-Jan-87 15:06:47 EST
Article-I.D.: glacier.13905
Posted: Sat Jan  3 15:06:47 1987
Date-Received: Sat, 3-Jan-87 21:54:19 EST
References: <653@imsvax.UUCP> <196@unisoft.UUCP> <2839@gitpyr.gatech.EDU>
Reply-To: jbn@glacier.UUCP (John B. Nagle)
Organization: Stanford University
Lines: 52
Keywords: databases, mainframes, Tandem, IBM


      One problem with mainframe databases is that IBM's main offering,
IMS, is single-thread.  Somewhere everything has to go through one hole 
to make the locking, logging, and fault recovery work right.
The biggest IBM CPUs available are not big enough to handle the entire
transaction volume of a major money center bank, and the software does not
support ganging CPUs together to solve this problem.  This is why, for
example, a number of the big banks have strange quirks in their on-line
systems, such as different balances at the ATM and teller terminals.
In fact, many of the "on-line" banking systems really do their updates
off line on other machines late at night and then load the database into
the on-line system.  

      If one were very clever, it would be possible to build on-line
database and transaction processing systems out of many small machines
in such a way as to get around this problem.  Someone has been.  Tandem.
Tandem is very serious about fault tolerance.  Some years ago they took
on the task of developing a relational database and transaction processing
system that would support distributed and replicated databases in a fault
tolerant manner.  They succeeded.  Their system can survive CPU failures,
disk failures, entire site failures in a multi-site network, and
can put itself back together when the equipment is repaired or replaced.
A by-product of this effort was that their system, being fully distributed,
can be scaled up to very large sizes, hundreds or thousands of processors.
Significantly, in the Tandem world, one can add new equipment without 
shutting down the system.  And not just trivial amounts of equipment,
either, new CPUs, memory, disks, entire sites can be added without a
shutdown.  Tandem installations have even been moved from one site to
another without a shutdown, by installing some loaned equipment at the
new site, interconnecting the systems with a wideband link, allowing the
databases to come into synchronization, moving disks and CPUs one at a
time from the old site to the new site, and switching over terminal lines
from the old to new site as the capacity of the new site increased.

      As an example of the power of this concept, when Wells Fargo Bank,
whose ATM system is controlled by Tandem machines, acquired Crocker Bank,
with IBM iron controlling the ATMs, the Crocker ATMs were cut over to the
Wells system without a shutdown of the Wells system, which runs 24 hours
a day, every day.  

      J.C. Penney is installing the world's largest Tandem network.
The big banks are watching this carefully.  The rise of interstate banking
is outrunning IBM's ability to service it.  This has been scary for some
D.P managers who have grown up with "No one was ever fired for picking
IBM" as their watchword.  Now they may have to tell their management
"We can't integrate our operations if we acquire that other bank; IBM
doesn't make a big enough machine."  Interesting.

					John Nagle

large sizes, hundreds or thousands of processors.  
of processors.