|
While the computing
environment of the 1990s is characterized by widely
distributed systems, it is important to understand
that this decentralized database approach is a
relatively new phenomenon.
It is very important to
understand that client-server does much more than
distribute data across a network. One of the
foremost reasons for using client-server is to share
the processing load between the client and the
server. There are two extremes that serve to
illustrate this point.
In the four quadrants of
this graph, we see several common approaches to the
distribution of Oracle data and processors. All
systems fall somewhere within this domain depending
on the amount of distributed processing and
distributed databases and the Oracle solution allows
any of these approaches.
1. Centralized data,
Centralized processing (No Networking)
This is the traditional
approach to Oracle data where all of the data
resides in a common database and all of the
processing is performed by a centralized computer,
usually a large UNIX server. This approach has the
advantage of better control of the Oracle data, but
has the disadvantage of being subject to widespread
performance degradation when the CPU becomes
overloaded. There is also a single point of failure
where a CPU problem could cripple the entire
system.
2. Centralized data,
distributed processing (Oracle Parallel Server)
This is a configuration
where the data resides in a central, controlled
environment, but the processing is distributed
across a network of remote CPUs. The main advantage
to this approach is the control over the data and
the ability to have redundant CPUs for extra
reliability and scalability. The main disadvantage
is that the Oracle database becomes a single point
of failure, and a runaway Oracle task could
slow-down the entire system. Oracle implements this
approach with its Oracle Parallel Server (OPS)
product.
3. Distributed data,
centralized processing (Oracle networking)
This is a common approach
for geographically distributed Oracle systems. A
centralized processor does all of the work, while
remote data hubs access the data. The computers at
the remote nodes act only as data servers with all
of the processing being done by a large central
processor. The main advantage to this approach is
the proximity of the data to the user in a
distributed network, and the main disadvantage is
the lack of centralized control over backup and
recovery of the data. This is the standard SQL*Net
and Net8 configurations.
4. Distributed data,
distributed processing (OPS with Net8)
This is the approach of many
Oracle8 systems, whereby both the data as well as
the processing are distributed across a network.
The primary advantage to this approach is the
ability to assign both data and processors on an
as-needed basis. The main disadvantage is the
problem of coordinating backup and recovery of the
data across all of the distributed nodes. This is
implemented with Oracle Parallel Server with Net8
interfaces to remote databases. |
