jbn@glacier.STANFORD.EDU (John B. Nagle) (01/03/87)
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. news@cit-vax.Caltech.Edu (Usenet netnews) (01/04/87)
Organization : California Institute of Technology Keywords: databases, mainframes, Tandem, IBM From: tim@tomcat.Caltech.Edu (Tim Kay) Path: tomcat!tim In article <13905@glacier.STANFORD.EDU> jbn@glacier.UUCP (John B. Nagle) writes: > > 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 > > [deleted] > > 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. John, Your information on Tandem was fascinating. I am no expert in databases, and I was supporting my arguments off the cuff. I was hoping that somebody would prove me wrong because IBM has used the "might makes right" idiom too long. What type of computers does Tandem use? Could you estimate for us how each of their nodes compares to a current day AT or Compaq 386? I have maintained all along that IBM would some day lose the mainframe market due to their crufty old software. Perhaps, the day of reckoning is closer than I thought. Timothy L. Kay tim@csvax.caltech.edu Department of Computer Science Caltech, 256-80 Pasadena, CA 91125
mat@amdahl.UUCP (Mike Taylor) (01/04/87)
In article <13905@glacier.STANFORD.EDU>, jbn@glacier.STANFORD.EDU (John B. Nagle) writes: > > One problem with mainframe databases is that IBM's main offering, > IMS, is single-thread. This is simply not true. Much of the rest of the article, which is a paean to Tandem's systems, is true. However, one should not overlook the compromises which Tandem makes in important areas such as "hot spot" and batch support. I am aware of IMS systems, BTW, in which 40+ large systems are coupled via ISC to support a single large application. Tandem makes a good product which has enjoyed deserved success in suitable applications. It is not, however, the answer to every problem. -- Mike Taylor ...!{ihnp4,hplabs,amd,sun}!amdahl!mat [ This may not reflect my opinion, let alone anyone else's. ]