Compaq Reliable Transaction Router manual Three-Layer Model, Three Layer Model

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The Three-Layer Model

Figure 2–1 The Three Layer Model

Terminals

Frontends (FE)

FE

Client

FE

Client

FE

Client

FE

Client

Routers (TR)	Backends (BE) Database (DB)

	BE
	Server

	BE	DB
	BE
	Server	DB
		DB
TR		DB
	BE	DB
	BE
	Server
TR

ZKO-GS011-99AI

•Allows performance or geographic expansion while protecting the investments made in existing hardware and application software.

The router layer contains no application software unless running callout servers. This layer reduces the number of logical network links required on frontend and backend nodes. It also decouples the backend layer from the frontend layer so that conﬁguration changes in the (frequently changing) user environment have little inﬂuence on the transaction processing and database (backend) environment.

The three layer model can be mapped to any system topology. More than one role may be assigned to any particular node. For example, on a system with few frontends, the router and frontend layers can be combined in the same nodes. During application development and test, all three roles can be combined in one node.

The nodes used by an application and their conﬁguration roles are speciﬁed using RTR conﬁguration commands. RTR lets application code be completely location and conﬁguration independent.

2–2Architectural Concepts

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Contents Reliable Transaction Router Getting Started Page Contents Reliability Features Figures Page Preface Purpose of this DocumentDocument Structure Related Documentation For all usersReading Path Readers CommentsSystem Manager Application Programmer If V2 to= Tutorial Introduction Reliable Transaction RouterRTR Continuous Computing Concepts RTR Continuous Computing ConceptsRTR Terminology RTR TerminologyClient Symbol Server Symbol Roles Symbols Components in the RTR Environment Nontransactional messaging Transaction ID Controller Database Server Application PresentationBusiness Logic Odbc Model PC Browser RTR FrontendBrowser Journal11 RTR Deployed on Three Nodes 12 Standby Server Conﬁguration 13 Transactional Shadowing Conﬁguration RTR Server Types RTR Server TypesStandby server Standby in a cluster 15 Standby Servers 16 Shadow Servers 17 Concurrent Servers Server1 Server2 Server3 Server4Transaction Partition a19 Bank Partitioning Example Standby Server Conﬁgurations Anonymous clients Tunnel RTR Networking Capabilities RTR Networking CapabilitiesPage Architectural Concepts Three-Layer ModelThree-Layer Model Three Layer ModelRTR Facilities Bridge the Gap BroadcastsFlexibility and Growth RTR Facilities Bridge the GapTransaction Integrity Flexibility and GrowthPartitioned Data Model Object-Oriented ProgrammingPartitioned Data Model Object-Oriented Programming Partitioned Data ModelObjects Functional and Object-Oriented Programming ComparedMessages Class Relationships Example 2-1 Objects-Deﬁned SamplePolymorphism Object Implementation Beneﬁts XA Support XA SupportReliability Features ServersFailover and Recovery Recovery ScenariosFailover and Recovery Backend Recovery Router Recovery Frontend Recovery Recovery ScenariosPage RTR Interfaces RTR Management Station RTR Management Station RTR Create Facility DESIGN/ALLROLES=NODEA RTR RTRRECEIVEMESSAGE/TIME=0 RTR RTRSTARTTX/CHAN=C Application Programming Interfaces InterfaceApplication Programming Interfaces RTR Browser InterfaceRTR C Example of an open channel call in an RTR client program RTR Environment RTR System Management EnvironmentRTR System Management Environment RtrcomservRTR System Management Environment Management Station Running Browser SoftwareMonitoring RTR RTR Runtime Environment RTR Runtime Environment Client ApplicationOptional External Applet Not Running Whats Next? Whats Next?Page Glossary Branch BroadcastCallout server ChannelCommon classes Concurrent serverData marshalling Data objectFault tolerant EndianEvent Event drivenFrontend InquorateJournal Key rangeMessage Message handlerMultichannel MultithreadedPrimary ProcessProperties Property classesRollback RouterRTR conﬁguration RTR environmentShadow StandbyTransaction Transaction controllerTwo-phase commit Transactional messageTransactional shadowing Index Index-1Index-2