NonStop Systems Introduction

The Application Server Environment
NonStop Systems Introduction— 527825-001
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Server Handling
Server programs can be written in any of the high-level languages supported by HP.
These include Java, C, and C++. (The specific languages that can be used depend on
which application server environment you are using.) Servers are central to the HP
support of standard component models. You can assemble server programs from third-
party components and design them to be independent of any particular platform. For
example, in the J2EE development environment, programmers use standard Java
development tools to write J2EE applications that can run on any platform compliant
with J2EE, including NonStop servers.
Server components are independent of the client platform. They can be connected to
browsers, PCs, and other devices by using standard protocols.
Load Balancing
The role of load balancing is to make sure that the response time of critical applications
remains fast and predictable, no matter how heavy the transaction volume at any given
time. To achieve load balancing, the application server automatically creates new
server processes in response to increased application workload.
The administrator can change configuration parameters to adjust the maximum
number of servers that are active at any one time and to balance the workload over the
server processes to help ensure optimal response time.
Without load balancing, the response time would vary with the transaction workload.
Response time would increase whenever the transaction rate went up, and would
decrease whenever the transaction rate went down. Load balancing helps to keep this
variation in response time to a minimum.
The application developer can also play a role in ensuring acceptable response time.
For example, if the same set of servers handles short and long transactions, some
requests for short transactions will be queued behind long transactions, resulting in
poor response times for short requests. To solve this problem, the developer can
Figure 3-7. Server Processes and Communication Paths
Clients
VST022.vsd
Process and link
management services
Application server environment
Application
Server A
Server B
Server C