Avoiding Common Bottlenecks - MACROMEDIA COLDFUSION 5-ADVANCED ADMINISTRATION Manual

Issues Affecting Successful Scalability Implementations
In this scenario, if the application uses an appropriate database concurrency
validation mechanism, then the HR Director would receive a message informing her
that she could not access the employee record because it was in use, thereby alerting
her that the HR Generalist is trying to change the record. However, if the application
did not use such a validation mechanism, the HR Director would overwrite the new
data that the Generalist had just entered, resulting in data integrity problems. This
simple example illustrates how important it is that your dynamic Web applications
handle database concurrency issues well.

Avoiding common bottlenecks

In addition to application design and construction considerations, you must also
plan accordingly to avoid common bottlenecks that can negatively affect a Web
application's performance.
Following are typical bottlenecks that can affect your application's ability to perform
and scale well:
Poorly written application logic Inefficient programming is probably the most
common reason applications perform poorly. Instituting industry best practices,
such as coding standards, design reviews, and code walkthroughs, can
significantly help to alleviate this problem.
Processor capacity Even a well-architected and programmed Web application
can perform poorly if the Web server's CPU is unable to provide sufficient
processing power. Make sure that heavy load, mission-critical applications reside
on hardware that can effectively do the job.
Memory Insufficient Random Access Memory (RAM) limits the amount of
application data that can be cached. Ensure that the amount of memory installed
on the application server machine is commensurate with the needs of the Web
application.
Server congestion Server congestion refers to all type of servers, not just the
Web server. Your application, proxy, search and index, and back office servers can
periodically experience high volume that indirectly degrades the performance of
your Web application. Therefore, when planning the physical design of the
system, be sure to investigate carefully the network topology that will be
implemented to ensure that existing servers are up to the task. If they are not, you
may need to add new servers to the topology to ensure uninterrupted service and
performance expectations.
Firewalls Some dynamic applications that must restrict anonymous access
because they present or share confidential information must pass through a
corporate firewall, which can slow down requests and responses. Make sure that
the correct ports are open on the firewall to ensure valid security authentication
and to enable appropriate client/server communications. (You may be able to
open additional secure ports to accommodate increased traffic.)
Network connectivity and bandwidth Consider the type of network your
application will run on (LAN/WAN/Internet) and how much traffic it typically
receives. If traffic is consistently heavy, you may need to add additional nodes,
routers, switches, or hubs to the network to handle the increased traffic.
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