Availability Guide for Application Design

What Is Application Availability?
Availability Guide for Application Design—525637-004
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System-Level Components
availability to ensure that its users can depend on its services. This concept is equally
true for the application as it is for the hardware, system software, and middleware.
Some of the major system-level components of availability are briefly introduced below,
followed by an introduction to the products that make up the transaction and database
services and their interfaces. Section 2, Overview of Server and Network Fault
Tolerance, provides more information about the system-level availability features.
Sections 4, 5, and 6 provide details about transaction and database services and how
they affect client/server and requester/server design.
System-Level Components
TNS/R and TNS/E systems offer the most flexible, cost-effective, and complete
availability features of any commercially available computer system.
The HP NonStop operating system manages the parallel hardware and provides an
Open System Services (OSS) interface for open systems products and applications
and a Guardian interface for traditional HP NonStop products and applications.
TNS/R availability is based on pairs of lock-stepped processors while the newer TNS/E
architecture is based on a looser lock-step between processors controlled by a logical
synchronization unit (LSU) that compares the output of processors before moving the
data onto the ServerNet fabric. See Section 2, Overview of Server and Network Fault
Tolerance for details.
Pairs of mirrored disks containing identical data provide for secure data. These disks
also provide a significant performance boost by allowing read operations to take place
Figure 1-1. The NonStop Application Environment
Pathway
Application
(Requester)
Pathway /iTS
NonStop Tuxedo/T
HP NonStop TS/MP, HP NonStop TMF
NonStop SQL/MP, Enscribe
OSS Guardian
Front-end
Application
Client
Component
of
Transaction
Monitor
Transaction
and Database
Services
System
API
Client
System
Tuxedo/WS
Open Application (Client) Other Client
HP
NonStop
System
Distributed
Computing
Environment
VST101.vsd
RSC/MP
TNS/R or TNS/E
Hardware
HP NonStop OS