processing a larger frame is only slightly more than the amount needed to process a smaller frame. If you use larger frames to transfer a single system message or block of data, decreases the total number of frames required to complete the transfer.

vThe values for IOP use in synchronous data link control (SDLC) environments do not necessarily increase consistently with the number of work stations or with the workload. An IOP can spend more time polling when the application is not using the line. It is possible to see a relatively high IOP use at low throughput levels.

vFor information on AS/400 configuration, see the Communications Configuration book.

vFor more information on performance tools, see the Performance Tools for AS/400 book.

Improving local area network performance

To achieve better performance with your AS/400 when communicating in a local area network (LAN), you need to consider the following.

v“Adjusting LANs for optimum communications performance”

v“Adjusting LAN lines for optimum communications performance”

v“LAN line speed considerations for IOPs” on page 10

Adjusting LANs for optimum communications performance

Local area networks (LAN) affect the communications performance on AS/400. Improvements to LAN input/output (IOPs) in the areas of increased central processing unit (CPU) time, IOP capacity, and support of IOP assist make them more efficient. This efficiency allows advanced program-to-program communications (APPC) to send request units to the IOP, passing the processing cost of processing frame to the IOP.

The following information can help you understand the protocol considerations for local area networks.

vA Data Link Control (DLC) can achieve a significantly higher data rate than other supported line types. This is due to the desirable combination of having a high media speed along with large frame sizes.

vWhen several sessions use a line or LAN concurrently, the aggregate data rate may be higher than when only one session is used.

vTo achieve good performance in a multi-user interactive LAN environment, you should manage the number of active users so that LAN media use does not exceed 50%. (A 25% utilization is recommended for Ethernet environments because of media collisions that causes the program to loop). Operating at higher utilization may decrease response time because of excess queueing time for the line. In a large transfer environment in which a small number of users contend for the line, a higher line use may still offer acceptable performance.

For more information about AS/400 configuration, see the Communications Configuration book.

Adjusting LAN lines for optimum communications performance

Several parameters in the line description (LIND) and the controller description (CTLD) play an important role in system performance that you can change.

The following information can help you to understand the line considerations for local area networks.

vMAXFRAME on the line description (LIND) and the controller description (CTLD): Maximizing the frame size in a LAN environment supplies the best performance for large transfers. A large frame size does not negatively affect performance for small transfers. Configure both the AS/400 system and the other link station for large frames. Otherwise, of the two maximum frame size values, the smaller is used when you transfer data. Bridges may also limit the maximum frame size. You should change the default value from 1994 to a larger size.

vLANMAXOUT on the CTLD (for advanced program-to-program communications (APPC) environments): This parameter governs how often the sending system waits for an acknowledgment. The LANACKFRQ

Chapter 3. Optimizing communications performance 9

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IBM AS/400 manual Improving local area network performance, Adjusting LANs for optimum communications performance
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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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