Chapter 4. Communications applications

Communications applications that are used in an APPC (advanced program-to-program) environment are also available to be used in an APPN and HPR environment; only the method by which data is transported is changed. APPC delivers the data from applications higher in the SNA layers down to APPN for transportation through the network. User-written APPC applications and distributed data management (DDM) are fully supported in an APPN and HPR environment. The topic, Application programming interface (API) performance considerations gives a more complete discussion of APPC applications.

When you encounter problems that indicate that the route to the remote location cannot be found, you can attempt to make the connection again with the Start Pass-Through (STRPASTHR) command. See the topic, Solving remote communication problems using STRPASTHR for more information.

For information on Connecting Windows 95/NT Clients to your AS/400, see Client Access.

User written APPC applications

APPN performs many functions in a communications environment. Therefore, it is important to consider time-out parameters in APPC programs which use ICF. In particular, it may be important to increase the WAITFILE parameter for these applications so that they do not time-out while waiting for APPN functions to be performed.

APPN function is transparent to APPC programs using APPN take advantage of the following routing functions:

vNon-adjacent nodes appear adjacent and so APPC programs may communicate directly to programs in non-adjacent nodes (without any APPC programs on the intermediate nodes).

vPerformance is improved for APPC programs with session endpoints that are not physically adjacent in the network.

vAPPC programs may communicate directly to programs in nodes in an adjacent APPN network through network nodes.

Distributed data management (DDM)

DDM is a function of the operating system that allows an application program or user on one system to use database files stored on remote systems. The systems must be connected by a communications network, and the remote systems must also be using DDM.

DDM on the AS/400 allows application programs or users to:

vAccess data files that reside on remote systems (target systems). The remote systems can also access data files on the local AS/400 system.

vAn application can add, change, and delete data records in a file that exist on a target system.

vCreate, delete, or rename files on a remote system.

vCopy a file from one system to another.

When DDM is in use, neither the application program nor the program user needs to know if the file that is needed exists locally or on a remote system. Remote and local file processing are essentially handled the same way.

Application program interface (API) performance considerations

To achieve better performance with your AS/400, you need to consider the application programming interface (API) available on the AS/400. To optimize APPC performance, consider the following:

© Copyright IBM Corp. 1998, 2001

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IBM AS/400 manual Communications applications, User written Appc applications, Distributed data management DDM
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AS/400 specifications

The IBM AS/400, now known as the IBM iSeries, is a midrange computer system that has been a cornerstone of enterprise computing since its introduction in 1988. Designed to provide a robust platform for business applications, the AS/400 is celebrated for its reliability, scalability, and integrated database capabilities.

One of the key features of the AS/400 is its Integrated Operating Environment, which blends hardware and software resources seamlessly. This integration allows businesses to execute diverse workloads, ranging from traditional applications to modern web-based services, all on a single platform. The operating system, OS/400 (now IBM i), offers a rich set of APIs and tools for developers, simplifying application development and management.

Another standout characteristic of the AS/400 is its built-in database, DB2 for i. This powerful relational database management system allows for efficient data handling and provides advanced features such as support for SQL, XML, and JSON, making it easier for businesses to manage their data and integrate it with other systems. The database's tight integration with the operating system enables high performance and security.

In terms of scalability, the AS/400 can accommodate small businesses as well as large enterprises, with the ability to support hundreds of users simultaneously. Its architecture allows for easy upgrades in hardware, meaning that organizations can scale their systems without replacing the entire infrastructure.

Security is another critical attribute of the AS/400. With a sophisticated security model, it offers built-in user authentication, access control, encryption, and auditing capabilities to protect data and applications from unauthorized access.

The AS/400 also supports multiple programming languages, including RPG, COBOL, Java, and PHP, giving organizations the flexibility to choose the development tools that best fit their needs. This diversity helps maintain legacy applications while also developing new ones that leverage modern technologies.

Moreover, the platform supports both traditional green-screen interfaces and modern graphical user interfaces, allowing organizations to transition smoothly into contemporary user experience paradigms.

Overall, the IBM AS/400 stands out as a resilient, flexible, and secure computing platform that enables organizations to effectively manage their business operations, streamline processes, and adapt to changing market demands. Its unique combination of integrated features and capabilities ensures that it remains relevant in today's fast-paced technology landscape.
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