Introducing BEA eLink TCP for Tuxedo


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The BEA eLink for Mainframe TCP for Tuxedo (hereafter referenced as eLink TCP for Tuxedo) product is a domains-based gateway connectivity feature that allows application programs on BEA Tuxedo systems to perform non-transactional tasks with application programs in other OLTP systems that support eLink TCP for Tuxedo gateways. These include:

CICS on IBM MVS systems
IMS/TM on IBM MVS systems

The eLink TCP for Tuxedo gateway is designed to provide transparent access to services that reside outside a BEA Tuxedo region. In addition, eLink TCP for Tuxedo can provide remote application programs with access to local services.

This document provides information about the following topics:

BEA eLink TCP for Tuxedo and the BEA Tuxedo Architecture

A BEA Tuxedo region consists of client and server programs that operate across a network of BEA Tuxedo systems or compatible systems. Any client program can request services that are offered by any server program running on any computer in the region. The location of server programs is kept transparent through use of a directory that maps services to servers.

As Figure 1-1 shows, eLink TCP for Tuxedo extends this transparent access by sending requests to and receiving requests from remote regions and systems through TCP/IP network software.

Figure 1-1 Routing Service Calls through BEA eLink TCP for Tuxedo

As Figure 1-1 illustrates, inside a single region, eLink TCP for Tuxedo fits between the BEA Tuxedo software and TCP/IP.

When local client programs send requests to remote systems, eLink TCP for Tuxedo transforms those requests into messages formatted appropriately for transmission to the remote system. Also, when remote systems respond, eLink TCP for Tuxedo transforms these responses into replies that local client programs can process.
When remote client programs send request messages, eLink TCP for Tuxedo transforms those messages into requests that local service routines can process. Also, when local service routines send replies, eLink TCP for Tuxedo transforms those replies into messages that remote services can process.

The eLink TCP for Tuxedo product is implemented as a Tuxedo domain gateway. It accepts standard BEA Tuxedo service requests and returns standard replies.

One eLink TCP for Tuxedo gateway connects to multiple communications targets, also referred to as gateways. Each communications target, or gateway, is a unique network endpoint.

Although remote systems are identified in the eLink TCP for Tuxedo configuration, they remain unknown to BEA Tuxedo software. For example, remote systems that are accessible through eLink TCP for Tuxedo are not identified in the MACHINES section of the UBBCONFIG file.

The eLink TCP for Tuxedo gateway maintains its own control information in shared memory, in much the same way that BEA Tuxedo software itself maintains the Bulletin Board. Although eLink TCP for Tuxedo accesses the BEA Tuxedo Bulletin Board, BEA Tuxedo does not access eLink TCP for Tuxedo control information.

Operational Considerations

Operational considerations are permanent limitations on using a feature. The following operational considerations apply to eLink TCP for Tuxedo:

Note: In the following discussion, a local application program is one that resides within the immediate BEA Tuxedo administrative region. A remote application program is one that resides outside the immediate BEA Tuxedo administrative region.

The eLink TCP for Tuxedo software does not support conversational communication.
The eLink TCP for Tuxedo software supports only nontransactional communication.
Local client and server programs which use the tpsprio() function set the priority where service requests are dequeued by eLink TCP for Tuxedo. This process does not affect any prioritization on the remote system.
Local client programs cannot use the tpbroadcast() function to send unsolicited messages to remote client programs (and the reverse).
Local services cannot use the tpbroadcast() or tpnotify() functions to send messages to remote client programs (and the reverse).
When local client and server programs use the tpgprio() function to determine the priority of a remote service, the priority of a local eLink TCP for Tuxedo requester is returned.

For background information about these operational considerations, see Understanding How BEA eLink TCP for Tuxedo Works.

BEA eLink TCP Functionality

The following functionality is available in this version of eLink TCP.

Domains-based Gateway Connectivity

The eLink TCP product has a domains-based architecture supporting bidirectional communications, request/response support, and support for MVS Open Transaction Manager Access (OTMA) interfaces.

Security

The eLink TCP for Tuxedo product grants access to BEA Tuxedo services based on a user name that the remote gateway supplies.

The eLink TCP for CICS product can initiate transactions or link to programs. BEA Tuxedo security provides the user ID value to the eLink TCP product to test for appropriate security prior to initiating the transactions.

The eLink TCP for IMS product has an OTMA interface that supports enhanced security. This interface allows a BEA Tuxedo requester to pass a user ID through the OTMA server interface for authorization through a third-party security package, such as RACF.

Connection Multiplexing

The eLink TCP for Tuxedo allows multiple requests to process simultaneously over a single connection. This feature is known as connection multiplexing. Two connecting gateways determine a multiplex count that is acceptable to both sides at connection time. After establishing the connection, clients can send multiple requests (up to the number in the multiplex count) to the server gateway. Connection multiplexing allows for more efficient use of sockets and other system resources by the eLink TCP gateways.

Note: Each connection is one-directional, which means clients on opposing platforms cannot use the same connection to communicate with remote servers.

Domain Name Server Support

The eLink TCP product supports domain name server (DNS) resolution of IP addresses. This support allows you to change the IP address at the Domain Name Server to implement address changes without reconfiguring the eLink TCP gateway.

GWIDOMAIN Gateway Component

The eLink TCP product consists of a single component, the GWIDOMAIN gateway. This gateway is responsible for the mediating both incoming and outgoing requests. It also maintains connections with all remote gateways.

How eLink TCP for Tuxedo Affects BEA Tuxedo Application Programs

The eLink TCP for Tuxedo product preserves the high degree of location transparency that BEA Tuxedo software provides. In fact, in virtually all cases, programmers do not need to know that particular services are provided by remote systems.

The eLink TCP for Tuxedo product supports the main BEA Tuxedo communication paradigm: request/reply communications (either synchronous or asynchronous).

All BEA Tuxedo buffer types can be employed for data exchange. These include:

X/Open standard XATMI buffer types
BEA Tuxedo ATMI buffers

Each of the three X/Open buffer types is equivalent to a BEA Tuxedo ATMI buffer type. The following information provides these equivalencies.

X_OCTET is equivalent to CARRAY
X_C_TYPE is equivalent to VIEW
X_COMMON is equivalent to VIEW, but represents only the subset of field types that are common to both the C and COBOL languages

VIEW Definitions

In some circumstances, you must convert typed buffers to formats that are acceptable to target systems. The standard BEA Tuxedo system VIEW definition mechanism is employed for this purpose.

VIEW definitions make it possible to map input data and output data between different programming environments (such as C and COBOL). They also enable eLink TCP for Tuxedo to convert data representations automatically between different systems.

VIEW definitions can be created by programmers or system administrators. See the Configuring BEA eLink TCP for Tuxedo for Data Mapping section for details. For more detailed information about programming considerations, see the Understanding How BEA eLink TCP for Tuxedo Works section.

FML Buffer Support

When communicating with systems or regions that do not support FML buffers directly, the eLink TCP for Tuxedo gateway can convert FML buffers to or from user-defined record layouts in a manner transparent to the FML application. Thus, once a VIEW definition that describes the remote application's record layout is created, it can be used to convert the record to or from an FML buffer. The GWICONFIG (eLink TCP for Tuxedo configuration file) and DMCONFIG files contain VIEW specifications as part of the service description.

Through this conversion between ATMI buffers and record structures, eLink TCP for Tuxedo supports sending fielded buffers containing FML data between regions. The eLink TCP for Tuxedo software converts the data from FML buffers to user-defined records using the VIEW definitions and field descriptions at the originating region.

You can use an alternate data mapping tool to map FML buffers to formats that mainframe applications can use. For more information about how to configure eLink TCP for Tuxedo to work with an alternate data mapping tool, see the Configuring BEA eLink TCP for Tuxedo for Data Mapping and Configuring BEA eLink TCP for Tuxedo sections.

How eLink TCP for Tuxedo Affects BEA Tuxedo Administration

The eLink TCP for Tuxedo administration tools and features are thoroughly integrated with BEA Tuxedo administration tools and features. Here are some specific examples:

System administrators define eLink TCP for Tuxedo in the BEA Tuxedo configuration as a regular Tuxedo domain gateway.
The eLink TCP for Tuxedo domain configuration file (DMCONFIG) specifies how local BEA Tuxedo service names are mapped to remote service names. Also, the GWICONFIG file identifies VIEW definitions that eLink TCP for Tuxedo uses to convert and translate input and output data.
At runtime, system administrators use BEA Tuxedo subcommands to manage eLink TCP for Tuxedo and related processes.

For more detailed information about configuring eLink TCP for Tuxedo, see the Configuring BEA eLink TCP for Tuxedo section. For detailed information about commands for administering eLink TCP for Tuxedo,see the BEA Tuxedo Administrator's Guide and the BEA Tuxedo Domain User Guide.