Managing Multiple Databases Across Heterogeneous Hardware and Software Systems - High-Performance Web Databases: Design, Development, and Deployment - page 479

almost certain that no amount of technical prowess will compensate.
There are two main initiatives in the planning phase of the functional data-
base bridge:

• Evaluations of the existing communications infrastructure, available ex-

pertise, and commercial middleware. These evaluations are primarily

technical in nature, although management will have some influence
because new capabilities may be indicated. For example, if the current
communications infrastructure is deemed inadequate, management
must approve the building of the new abilities.

• Designations of master databases, update frequency, and data owner-

ship. These designations, although influenced by technical consider-

ations, are primarily management decisions and represent points that
could materially alter business practices.

An evaluation of the exist-
ing communications infrastructure should establish the following infor-
mation:

Evaluating the Communications Infrastructure.

• The available communications paths between the databases. This may

be a LAN, WAN, T1 line, batch tape, queuing system, or any other way
to move the information between systems.

• The security of the communications paths . Because there will now be

transaction flow from one database to another, security consider-
ations are important. For example, if the proposed communications
channel is a T1 line from another city, it can be considered secure. If,
however, the proposed channel is over a UNIX system that is connect-
ed to the Internet (without a firewall), then steps should be taken to
qualify all incoming transactions before an update (or any other ac-
tion, for that matter) is applied.

• The stability of the communications paths. How reliable is the channel?

How often does it go down?

• The current load on the communications channel. Is there enough band-

width to accommodate the new transaction load? This evaluation ne-
cessitates an estimate of transactions per unit time.

• Failure analysis of the communications channel. What are the ramifica-

tions if the communications carrier should fail? And how long can that
failure continue before there are serious ramifications?

• Communications protocols. Some smaller (or older) systems do not na-

tively possess modern communications protocols. The choices in this
case are either to custom-build an interface to the database, perhaps
with vendor assistance (though adding a modern communications
protocol to a system can be complicated), or to drop back to a less am-
bitious communications protocol — for example, batch tape transfer
instead of TCP/IP transfer.