IBM AS-400 User Manual

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ERserver

iSeries

Networking

iSeries Communications Management

ERserver

iSeries

Networking

iSeries Communications Management

© Copyright International Business Machines Corporation 1998, 2001. All rights reserved.

US Government Users Restricted Rights – Use, duplication or disclosure restricted by GSA ADP Schedule Contract with IBM Corp.

Contents

Part 1. Getting started with AS/400 communications

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Chapter 1.

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Chapter 2.

Configuring AS/400 for communications . . . .

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Creating a network interface description . . . . . . . . .

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Creating a network server description . . . . . . . . . .

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Creating a line description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Chapter 3. Optimizing communications performance . . . . . . . . . . . .

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Improving wide area network performance . . . . . . . . . . . . . . . . . .

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Adjusting WAN protocols for optimum AS/400 performance . . . . . . . . . .

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Adjusting the WAN line speed for optimum AS/400 performance. . . . . . . . .

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WAN line speed considerations for IOPs . . . . . . . . . . . . . . . . .

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Improving local area network performance . . . . . . . . . . . . . . . . . .

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Adjusting LANs for optimum communications performance . . . . . . . . . . .

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Adjusting LAN lines for optimum communications performance . . . . . . . . .

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LAN line speed considerations for IOPs . . . . . . . . . . . . . . . . . .

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Improving data path performance . . . . . . . . . . . . . . . . . . . . .

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Considerations for subsystem configuration for error recovery performance . . . . .

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Communications performance considerations for interactive jobs . . . . . . . . .

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Communications performance considerations for batch jobs . . . . . . . . . . .

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Mixing interactive and batch jobs on a WAN line . . . . . . . . . . . . . . .

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Performance considerations for AnyNet communications . . . . . . . . . . . .

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Subsystems . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Chapter 4. Communications applications . . . . . . . . . . . . . . . . . .

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User written APPC applications . . . . . . . . . . . . . . . . . . . .

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Distributed data management (DDM) . . . . . . . . . . . . . . . . . .

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Application program interface (API) performance considerations . . . . . . . .

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Performance considerations for intersystem communications function . . . . .

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Performance considerations for Common Programming Interface Communications

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Chapter 5. Communicating with host systems . . . . . . . . . . . . . .

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Matching AS/400 parameters for a host system . . . . . . . . . . . . . .

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Matching AS/400 line description parameters for a host system . . . . . . .

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Matching AS/400 controller description parameters for a host system . . . . .

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Matching AS/400 device description parameters for a host system . . . . . .

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Matching AS/400 mode and class-of-service description parameters for a host system . . . . . . 25

Configuring dependent LU requester (DLUR) . . . . . . .

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Configuring the host controller description . . . . . . .

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Configuring the device descriptions . . . . . . . . . . . . . . . . . . . . . . . . . 31

Chapter 6. Communicating with a remote AS/400 system . . . . . . .

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Matching AS/400 line description parameters for a remote AS/400 system . .

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Matching AS/400 controller description parameters for a remote AS/400 system

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Matching AS/400 device description parameters for a remote AS/400 system .

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Connecting one AS/400 to another AS/400 system . . . . . . . . . . .

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Chapter 7. Communicating with remote workstation controllers . . . . .

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Matching AS/400 parameters for 5494 controllers. . . . . . . . . . . .

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Matching AS/400 parameters for a 5494 connected by token-ring . . . . .

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Matching AS/400 parameters for a 5494 connected by Ethernet . . . . .

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© Copyright IBM Corp. 1998, 2001

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Matching AS/400 parameters for a 5494 connected by frame relay . . . . . . . . . . . .

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Matching AS/400 parameters for a 5494 connected by SDLC . . . . . . . . . . . . . .

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Matching AS/400 parameters for a 5494 connected by X.21 . . . . . . . . . . . . . . .

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Matching AS/400 parameters for a 5494 connected by X.25 . . . . . . . . . . . . . . .

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Matching AS/400 parameters for 3x74 controller . . . . . . . . . . . . . . . . . . . .

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Matching AS/400 parameters for a 3174 controller . . . . . . . . . . . . . . . . . .

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Matching AS/400 parameters for a 3274 controller . . . . . . . . . . . . . . . . . .

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Matching AS/400 parameters for finance controllers . . . . . . . . . . . . . . . . . . .

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Matching AS/400 parameters for 470x finance controllers . . . . . . . . . . . . . . . .

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Matching AS/400 parameters for FBSS finance controllers . . . . . . . . . . . . . . .

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Matching AS/400 parameters for retail controllers . . . . . . . . . . . . . . . . . . . .

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Matching AS/400 parameters for 3651 retail controllers . . . . . . . . . . . . . . . .

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Matching AS/400 parameters for 3684 retail controllers . . . . . . . . . . . . . . . .

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Matching AS/400 parameters for 4680/4690 LINE parameter . . . . . . . . . . . . . .

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Matching AS/400 parameters for 4680/4690 LINK parameter . . . . . . . . . . . . . .

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Matching AS/400 parameters for 4684 retail controllers . . . . . . . . . . . . . . . .

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Chapter 8. Troubleshooting communications problems . . . . . . . . . . . . . . . .

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Displaying message queues to solve communication problems . . . . . . . . . . . . . . .

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Displaying the Product Activity Log to solve communication problems . . . . . . . . . . . .

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Displaying the Print Error Log to solve communication problems . . . . . . . . . . . . . .

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Job logs and communication problems . . . . . . . . . . . . . . . . . . . . . .

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Solving communication problems using communications trace . . . . . . . . . . . . . . .

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System service tools and communication problems . . . . . . . . . . . . . . . . . .

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Trace Common Programming Interface (CPI) Communications (TRCCPIC) command . . . . .

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Solving communication problems using the system problem log . . . . . . . . . . . . . .

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Solving communication problems using status information . . . . . . . . . . . . . . . .

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Considerations for system tuning during error recovery. . . . . . . . . . . . . . . . . .

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Using error messages to aid in error recovery . . . . . . . . . . . . . . . . . . . . .

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Solving communication problems using reason codes . . . . . . . . . . . . . . . . . .

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Chapter 9. Networking concepts . . . . . . . . . . . . . . . . . . . . . . . . .

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Advanced Peer-to-Peer Networking . . . . . . . . . . . . . . . . . . . . . . . . .

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Advanced program-to-program communications

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Dependent LU requester support . . . . . .

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High-performance routing . . . . . . . .

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HPR architecture option sets . . . . . . . . . . . . . . . . . . . . . . . . . . . 89

Internetwork packet exchange support . . . .

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What is Systems Network Architecture. . . .

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What is TCP/IP . . . . . . . . . . . .

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Chapter 10. Common networking standards

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Local area network standards . . . . . . .

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ATM on AS/400 . . . . . . . . . . .

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Distributed data interface network . . . .

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Ethernet networks . . . . . . . . . .

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Token-ring networks . . . . . . . . .

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Wireless network . . . . . . . . . .

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Wide area network standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93

Asynchronous communications . . .

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Binary synchronous communications .

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Frame relay networks . . . . . . . . . . . . . . . . . . . . . . . . . .

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Integrated services digital network . . . . . . . . . . . . . . . . . . . . .

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Synchronous data link control network . .

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X.25

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X.21

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iv Version 5

Part 1. Getting started with AS/400 communications

The AS/400 is an extremely versatile system for networking technologies, supporting a broad range of communication protocols. Protocols that are supported include TCP/IP, APPC, APPN, HPR, Remote workstation, asynchronous, and binary synchronous communications.

AS/400 communications configuration is done by either manually or automatically creating a set of configuration objects that represent the local and remote systems that are to communicate. The types of objects required for a communications configuration vary, depending on the type of communications being configured.

Many factors can affect the performance of the AS/400 in a communications environment. To achieve the best performance with your particular environment review the topics, Optimizing communications performance, and Communications applications.

You can configure your AS/400 system to communicate with another AS/400 system, a non-AS/400 system, or a remote controller. For information on how to do this, see the following:

vCommunicating with host systems

vCommunicating with a remote AS/400 system

vCommunicating with remote workstation controllers

Communication problems are inevitable and will probably be an issue as you manage your network. If you suspect that you are having communication problems, review the topic Troubleshooting communication problems.

Before beginning to work with AS/400 communications, you may want to review the topics, Chapter 9, “Networking concepts” on page 87 and Chapter 10, “Common networking standards” on page 91. Here, you can find information related to some of the technologies common to deploying modern networking solutions in an AS/400 environment.

© Copyright IBM Corp. 1998, 2001

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Chapter 1. Print this topic

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© Copyright IBM Corp. 1998, 2001

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Chapter 2. Configuring AS/400 for communications

Follow these steps to configure your AS/400:

1. Depending on the type of hardware you have, you may need to refer to the following topics:

vCreating a network server description

vCreating a network interface description

2.You define lines by creating line descriptions. Depending on your hardware, the lines may be attached to a network server, or a network interface.

Creating a network interface description

Network interface descriptions for asynchronous transfer mode (ATM), frame relay, and integrated services digital network (ISDN) protocols describe the communications interface.

To create a network interface description, do the following:

1.Type one of these commands on any AS/400 command line for the type of network interface you are

creating and press F4:

v Create Network Interface (ATM) (CRTNWIATM)

vCreate Network Interface (Frame Relay Network) (CRTNWIFR)

vCreate Network Interface Description for ISDN (CRTNWIISDN)

2.Use the on-line help information to choose the correct parameter values.

3.Press Enter. The network interface description is created.

Creating a network server description

A network server description describes which Integrated PC Server the local area network (LAN) and the application will be using.

To create a network server description, do the following:

1.Type the Create Network Server Description (CRTNWSD) command on any AS/400 command line and press F4.

2.Use the on-line help information to choose the parameter settings.

3.Press Enter. The network server description is created.

Creating a line description

You create line descriptions to describe the physical line connection and the data link protocol to be used between the AS/400 system and the network.

To create line descriptions, do the following:

1.Type one of these commands on any AS/400 command line to define the type of line you are creating

and press F4.

v Create Line Description (Ethernet) (CRTLINETH)

vCreate Line Description (Distributed Data Interface (DDI)) (CRTLINDDI)

vCreate Line Description (Frame Relay) (CRTLINFR)

vCreate Line Description for (IDLC) (CRTLINIDLC)

vCreate Line Description (Synchronous Data Link Control (SDLC)) (CRTLINSDLC)

vCreate Line Description (Token-ring) (CRTLINTRN)

vCreate Line Description (Wireless) (CRTLINWLS)

vCreate Line Description (X.25) (CRTLINX25)

2.Use the online help information to choose the correct parameter values.

3.Press Enter. The line description is created.

© Copyright IBM Corp. 1998, 2001

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Chapter 3. Optimizing communications performance

Many factors can affect the performance of AS/400 application programs. To achieve the best performance with your particular communications environment, you may want to review these topics:

vImproving wide area network (WAN) performance.

vImproving local area network (LAN) performance.

vImproving data path performance.

Improving wide area network performance

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

v“Adjusting WAN protocols for optimum AS/400 performance”

v“Adjusting the WAN line speed for optimum AS/400 performance”

v“WAN line speed considerations for IOPs” on page 8

Adjusting WAN protocols for optimum AS/400 performance

Wide area network (WAN) protocols affect the communications performance on AS/400. Let us use X.25 for our example. For each X.25 communications controller, the AS/400 has some processing limitation for the line, the line speed, and the total number of virtual circuits that can be used. Performance degradation can be reduced by observing these limitations.

To optimize AS/400 performance for wide area networks, perform these tasks:

vReduce the total number of frames by using larger frames.

vTo take advantage of these large frame sizes, change the MAXFRAME parameter on the line description (LIND) to reflect the maximum value. For X.25, increase the DFTPKTSIZE and MAXFRAME parameters to their maximum value.

vConfigure a WAN line as full-duplex to provide you with a higher throughput for applications that can take advantage of this mode. This can also provide higher throughput for multiple users.

vIncrease frame relay to capacity.

The data rate for a given protocol may increase as frame size increases. Under these circumstances, the central processing unit (CPU) and the input/output processor (IOP) do not do as much processing. Fewer and larger frames also make more efficient use of the communications line (higher effective data rate) because of fewer overhead bytes and line turn-arounds.

Frame relay has equivalent performance over RS449, X.21, and V.35 assuming equal line speeds and conditions. Frame relay performance (CPU time) is similar to or slightly better than Synchronous Data Link Control. For properly tuned large transfer applications, the CPU and IOP have no problem using the line speed to capacity.

For information about configuring AS/400 communications, see the Communications Configuration book.

Adjusting the WAN line speed for optimum AS/400 performance

In many cases, the communications line is the largest contributor to overall response time in the wide area network (WAN). Therefore, you should closely plan and manage its performance. In general, having the appropriate line speed is the key consideration for gaining the best performance.

To adjust the line speed for your wide area network, perform these tasks:

vCheck the difference in performance between half-duplex utilization and full-duplex utilization on the line description.

© Copyright IBM Corp. 1998, 2001

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vFor interactive environments, keep line use below 30% to maintain predictable and consistent response times. Exceeding 50% line use usually slows down response time. The line use can be measured with the AS/400 performance tools.

vFor large transfer environments, or for environments in which only a small number of users are sharing a line, increase line use to allow for acceptable response times.

vThe CPU usage for fractional T1 support and other high-speed WAN connections is similar to any other line that runs the same type of work. As the speed of a line increases from a traditional low speed to a high-speed or full T1/E1/J1 speed, performance characteristics may change as follows:

With interactive transactions, performance may be slightly faster.

With a large transfer, performance may be significantly faster.

With a single job, performance may be too serialized to use the entire bandwidth.

With high throughput, performance is more sensitive to frame size.

With high throughput, performance is more sensitive to application efficiency.

With synchronous data link control (SDLC), the communications controller CPU usage increases because of polling.

Additional considerations for adjusting the wide area network line speed are the following:

vA common misconception about the line speed of each attached communications line is that central processing unit (CPU) resource is used in a uniform fashion. Exact statements cannot be made about the number of lines that any given AS/400 model can support.

vMost communications applications use a lot of CPU resource (to process data, to support disk input and output) and communications line resource (to send and receive data or display I/O). The amount of line resource that is used is proportional to the total number of bytes that are sent or received on the line.

Some additional CPU resource is used to process the communications software to support the individual sends (puts or writes) and receives (gets or reads). Communications input/output processor resource is also used to support the line activity.

vWhen a single job is running disk operations or doing non-overlapped CPU processing, the communications link is idle. If several sessions transfer concurrently, then the jobs are more interleaved and make better use of the communications link.

vPolling is an important consideration for synchronous data link control (SDLC) environments. All SDLC polling is handled by the communications controller and is governed by parameters in both the line and controller descriptions.

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

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

WAN line speed considerations for IOPs

When configuring a communications controller, you should consider both subsystem storage and aggregate line speed. Subsystem storage is the amount of storage available on the communications controller. Aggregate line speed is the sum of individual lines speeds that are attached to the communications controller.

The following information can help you understand network line speed considerations for input/output processors (IOPs).

vFor interactive environments, you should not exceed 60% use on the communications IOP. Exceeding this threshold in a large transfer environment or with a small number of concurrent users may still offer acceptable performance. Use the AS/400 performance tools to get the utilization.

vYou can attach multiple IOPs to an AS/400 system. The maximum number of IOPs that can be attached is determined by the AS/400 model. It is important to distribute the work load across several IOPs if the performance capabilities of a single IOP is exceeded.

vEven though an IOP can support certain configurations, a given AS/400 model may not have enough system resource (for example, CPU processing capacity) to support the work load over the lines.

vThe use of larger frames generally improves large transfer performance in terms of capacity for the communications IOP and in terms of system response time. The amount of time that the IOP spends

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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

parameter value on one system should never have a greater value than the LANMAXOUT parameter value on the other system. The parameter values of the sending system should match the values on the receiving system.

vSetting appropriate values for the LANMAXOUT parameter along with the LAN acknowledgment frequency (LANACKFRQ) parameter for both the sending stations and receiving stations is essential for optimal performance. Other values may decrease throughput by 50% or even more if conditions trigger time-outs.

vLANWDWSTP for advanced program-to-program communications (APPC) on the controller description (CTLD): If there are network congestion or overruns to certain target system adapters, then increasing the value from the default of *NONE to 2 or more may improve performance.

In general, setting the LANMAXOUT parameter value to *CALC or 2 offers the best performance for interactive environments and adequate performance for larger transfer environments.

vFor large transfer environments, changing the LANMAXOUT value may significantly increase performance. As starting points, use the following guidelines:

When you are communicating with a recent model personal computer, increase the LANMAXOUT parameter, but keep the LANACKFRQ parameter set to *CALC. For older models of personal computers, use *CALC for both values to limit buffer overruns.

If LANACKFRQ and LANMAXOUT parameter values are changed without noticeable performance improvements, change the values back to *CALC.

For more information on AS/400 communications, see the Communications Configuration book.

LAN line speed considerations for IOPs

When configuring an AS/400 system with communications lines and local area networks (LANs), you should not overload an input/output processor (IOP) to prevent possible system performance bottlenecks.

The following information can help you to understand the line speed considerations for IOPs.

vThe integrated PC server performance is similar to the 2619 and the 2617 IOPs for host LAN functions. For send and receive scenarios, performance is equivalent. For large transfers, the 6506 IOP is slightly faster than the 2619 TRLAN IOP, but slightly slower than the 2617 Ethernet IOP. These differences are not significant enough to choose one over the other.

vThe 100 Mbps Ethernet support provides the best LAN performance. The IOP can be optimally configured to have an aggregate transfer rate of 27 Mbps. Multiple concurrent large transfers may be required to drive at that rate.

vWhen analyzing communications performance that includes the 2619 TRLAN IOP, you should be aware that resources other than the IOP use can become the bottleneck.

vYou should have the highest capacity IOP available for file serving. You should have the highest capacity IOP available for environments that use many communications input and output operations for each transaction. The highest capacity IOP also minimizes the overall response time.

See the following references for more detail:

vFor more information about AS/400 communications, see the Communications Configuration book.

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

Improving data path performance

To assess the performance of your data path, you may want to review the following topics:

vConsiderations for subsystem configuration for error recovery performance

vCommunications performance considerations for interactive jobs

vConsider communications performance for batch jobs

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vMix interactive and batch jobs on a wide area network line

vPerformance considerations for AnyNet communications

vSubsystems

Considerations for subsystem configuration for error recovery performance

Each piece of work that runs on the AS/400 system is called a job. Each job is a single, identifiable sequence of processing actions that represents a single use of the system. The basic types of jobs performed are interactive jobs, batch jobs, spooling jobs, autostart jobs, and prestart jobs.

Jobs that run in subsystems do all work that is performed on the AS/400. As the number of users on the system increases, it becomes important for you to consider how the communications and interactive subsystems should be configured.

The configuration of subsystems has little impact in normal data path operations. However, multiple subsystems can provide multiple processes to do cleanup and recovery when error conditions occur. This can result in improved performance.

As the number of users on the system increases, you must consider the importance of how subsystems are configured:

vConsider limiting the number of devices that are serviced by a single subsystem. Between 200 and 300 devices for each subsystem are recommended. Use the following recommendations to divide these users:

The number of users in any given subsystem

The connectivity used to access the system

The type of work the users do

The geographic location of the users

vCreate additional communications and interactive subsystems to split the work into multiple subsystems.

vThe work that is performed in the QCMN subsystem is for connecting and disconnecting from the system. Error recovery considerations are important in the configuration of the communications subsystem.

vTo prevent a subsystem from ever allocating a device, ensure that there are no workstation or type entries for the devices that you do what allocated by that subsystem.

vOnly use the AT(*ENTER) option if you must allow jobs to transfer into that subsystem.

vFor each subsystem you have defined, you need to identify which users will run in which subsystems. Use the Add Work Station Entry (ADDWSE) command and the Remove Work Station Entry (RMVWSE) command. You can set up work stations entries that identify which devices that subsystem should allocate, as well as which devices a subsystem should not allocate.

Note: You can use the ADDWSE commands while the subsystem is active. However, subsystems do not reallocate device locks dynamically. Eventually, it may be necessary to end and restart the subsystems to have the device locks allocated to the desired subsystem.

To specify the devices a communications subsystem should allocate:

ADDCMNE SBSD(libname/sbsname) DEV(devname*) MODE(modename)

To specify the devices a communications subsystem should not allocate:

ADDCMNE SBSD(libname/sbsname) DEV(devname*) MODE(modename) MAXACT(0)

Note: Database and file servers run only in QSERVER. Do not attempt to allocate sessions running over the QSERVER mode description. You can do this by adding the following communication entry to your subsystem:

ADDCMNE (SBSD(libname/sbsname) DEV(devname*) MODE(QSERVER) MAXACT(0)

See the following example for a way of configuring your communications subsystem.

Chapter 3. Optimizing communications performance 11

Example: Communications subsystem configuration

1.Create a duplicate of QCMN:

CRTDUPOBJ OBJ(QCMN) FROMLIB(QSYS) OBJTYPE(*SBSD) TOLIB(MYLIB) NEWOBJ(MYCMN)

2.Set up the communication entries:

ADDCMNE SBSD(MYLIB/MYCMN) DEV(PC*)

ADDCMNE SBSD(MYLIB/MYCMN) DEV(PC*) MODE(QSERVER) MAXACT(0)

ADDCMNE SBSD(QSYS/QCMN) DEV(PC*) MODE(QPCSUPP) MAXACT(0)

3. If desired, update your system startup program to start your new subsystems automatically.

Communications performance considerations for interactive jobs

An interactive job is one that uses a keyboard and character-type display. If a job needs the user to type on the keyboard and display character results, that job is probably considered interactive. Interactive in this sense means that the job and the user depend on each other to get the work done.

To optimize communications performance for interactive jobs, consider the following:

vAttach work stations through communications requires more CPU overhead than 5250 local workstations.

vUse a twinaxial controller to provide better performance than an American National Standard Code for Information Interchange (ASCII) controller.

vKeep the line utilization below 30 percent for best performance when interactive users are attached. This will maintain predictable and consistent response times. Exceeding 50 to 60 percent line utilization will usually cause unacceptable response times.

If your system has interactive users who are connected many different ways, you should consider configuring your interactive subsystems to separate the users. Local workstation, remote workstations, 5250 display station pass-through, or Telnet are some examples of these types of connections that should be separated. When you configure interactive subsystems, identify how you want the interactive users to be separated and create the appropriate subsystem descriptions.

During error recovery, when many users risk losing their sessions at one time, an interactive subsystem can be very busy performing device recovery. This device recovery can adversely affect the work of other users in the subsystem who would otherwise be unaffected by the failure. Therefore, you may need to change how the interactive subsystems are configured. However, multiple subsystems can provide multiple processes to do cleanup and recovery when error conditions occur. This can result in improved performance.

The example below shows how to configure an interactive subsystem to allocate devices that begin with devname* and present a signon display on those display devices:

ADDWSE SBSD(libname/sbsname) WRKSTNDEV(devname*) AT(SIGNON)

Use the following example to configure an interactive subsystem so that the device name devname* is not allocated and a signon display does not appear.

ADDWSE SBSD(libname/sbsname) WRKSTNDEV(devname*) AT(*ENTER)

Adding workstation entries with AT(*ENTER) allows you to use the Transfer Job (TFRJOB) function into that subsystem. If the TFRJOB function is not required or necessary, there is no need to add the workstation entries with AT(*ENTER).

To specify the devices an interactive subsystem should allocate when the subsystem is started:

ADDWSE SBSD(libname/sbsname) WRKSTN(devname*) AT(*SIGNON)

To specify the devices an interactive subsystem should not allocate when the subsystem is started:

ADDWSE SBSD(libname/sbsname) WRKSTN(devname*) AT(*ENTER)

v See the following example for a way of configuring your interactive subsystem.

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Example: Interactive subsystem configuration

1.Create a subsystem description:

CRTSBSD SBSD(MYLIB/MYINTER) POOLS((1 *BASE) (2 *INTERACT))

2.Create a class

CRTCLS CLS(MYLIB/MYCLASS) RUNPTY(20)

3.add routing entries to your subsystem:

ADDRTGE SBSD(MYLIB/MYINTER) SEQNBR(10) CMPVAL(QCMDI) PGM(QSYS/QCMD) POOLID(2) ADDRTGE SBSD(MYLIB/MYINTER) SEQNBR(9999) CMPVAL(*ANY) PGM(QSYS/QCMD) POOLID(2)

4.Create a job queue, and add the job queue entry to your new subsystem:

CRTJOBQ JOBQ(MYLIB/MYJOBQ)

ADDJOBQE SBSD(MYLIB/MYINTER) JOBQ(MYLIB/MYJOBQ) MAXACT(200)

5.Set up the workstation name entries. Remove all the *ALL workstation type entries first, and then add the appropriate workstation name entries:

RMVWSE SBSD(QSYS/QINTER) WRKSTNTYPE(*ALL) ADDWSE SBSD(QSYS/QINTER) WRKSTN(QPADEV*) ADDWSE SBSD(MYLIB/MYINTER) WRKSTN(PC*)

6.If desired, update your system startup program to start your new subsystems automatically.

Communications performance considerations for batch jobs

Each piece of work run on the AS/400 system is called a job. Each job is a single, identifiable sequence of processing actions that represents a single use of the system. The basic types of jobs that are performed are interactive jobs, batch jobs, spooling jobs, autostart jobs, and prestart jobs.

Batch jobs are predefined groups of processing actions that are submitted to the system to be performed with little or no interaction between the user and the system. Batch jobs can be tuned for optimized performance.

To optimize batch jobs for communications, consider the following:

vBreak the application into pieces and having multiple batch threads (jobs) operate concurrently.

vReduce the number of open and close operations, input and output operations.

vIf you have a considerable amount of main storage available, consider using the Set Object Access (SETOBJACC) command. This command preloads the complete database file, database index, or program into the assigned main storage pool if sufficient storage is available. The objective is to improve performance by eliminating disk-read/write operations.

vTry to limit the number of communications input and output operations by doing fewer (and perhaps larger) application sends and receives when communications lines are used.

vBlock the data in the application. Try to place the application on the same system as the frequently accessed data.

For more information about batch job performance, see the Communications Management book.

Mixing interactive and batch jobs on a WAN line

When interactive users and large transfers are running on a communications line concurrently, you may need to change configuration parameters. You should be able to configure AS/400 communications to work with interactive and batch jobs.

To mix interactive and batch jobs on a wide area network (WAN) line, consider the following to keep interactive performance acceptable:

vUse Advanced Peer-to-Peer Networking (APPN) transmission priority to prioritize the interactive user’s transfer over that of the large transfer. This is the preferred method to transfer batch and interactive jobs.

Chapter 3. Optimizing communications performance 13

vChange the request/response unit size to a lower value for the large transfer. This parameter setting optimizes response time at the expense of large transfer performance.

vReduce the pacing values for the large transfer to slow it down, which allows the interactive users more windows for getting on the line.

Note: The overall central processing unit time increases for the large transfer.

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

Performance considerations for AnyNet communications

AnyNet communications is a good performance factor for you to consider. It is more expensive to use than any of the OS/400 protocols because you spend twice as much to run two protocols.

To optimize AnyNet performance, consider the following:

vFor send and receive pairs, the most efficient use of an interface is with its own protocol stack. That is, intersystem communications function (ICF) and common programming interface communications (CPI Communications) perform the best with advanced program-to-program communications (APPC). There is additional CPU time when the crossover between the protocols processes.

vEach communications interface performs differently depending on the scenario. ICF and CPI Communications perform the best with APPC.

Note: An alternative to AnyNet communications is to have SNA and TCP/IP running parallel or over the same lines in your network. Hence, performance implications can be surpassed by not using AnyNet.

For more information about AnyNet/400 sockets, see the book Sockets Programming .

Setting up the AnyNet environment

AnyNet/400 is an AnyNet family product. These products allow you to use application programs that are written for a certain communications protocol but also run over non-native communications protocols without changing (or even re-compiling) the application program. The choice of the destination address controls whether the request is sent over the native protocols or through the AnyNet code and on to a non-native protocol.

To configure Transmission Control Protocol/Internet Protocol (TCP/IP) over advanced program-to-program communications (APPC), you need to take two basic actions:

1.Identify the set of IP addresses to route over the SNA network.

2.Tell the system how to convert the IP address to the SNA format.

For more information about APPC Over TCP/IP Configuration, see the APPC Programming book.

For more information about IPX Support, see the Internetwork Packet Exchange (IPX) Support.

For related information about AnyNet, see:

“AnyNet communications for the AS/400 system” “Performance considerations for AnyNet communications”

AnyNet communications for the AS/400 system

AnyNet is an IBM implementation of the Multiprotocol Transport Networking (MPTN) architecture, such as AnyNet/2 and AnyNet/Multiple Virtual Storage (MVS). AnyNet capability allows applications and associated services that use application programming interfaces, such as sockets, intersystem communications function (ICF), or CPI Communications, the flexibility to use alternative network protocols, such as Systems Network Architecture (SNA) or TCP/IP. AnyNet is a family of products that allow applications that

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are written for one type of network protocol to run over a different type of network protocol. For example, without AnyNet, your choice of application program interface (API) dictates your choice of network protocol, or your choice of network protocol dictates your choice of APIs.

AnyNet allows you to mix and match applications with network protocols. In fact, you can do this without changing your application programs. Your destination address (such as a remote location) determines the type of network protocol to use.

vAnyNet/400 Sockets

This support converts TCP/IP addresses to SNA addresses that are based on tables that are configured by the network administrator. Programs supported include File Transfer Protocol (FTP), Simple Mail Transfer Protocol (SMTP), Simple Network Management Protocol (SNMP), PING, and user-written sockets programs.

TCP/IP over SNA

TCP/IP over IPX

vAnyNet/400 APPC (advanced program-to-program communications)

This support allows programs that are written to traditional APPC APIs (such as ICF, CPI-Communications, and CICS/400) to be run over non-APPC networks. The application program uses Location names to specify the source and destination address. A TCP/IP domain name server converts these location names to IP addresses. Programs supported include distributed data management (DDM), Distributed Relational Database Architecture (DRDA), SNA distribution services (SNADS), display station pass-through, Client Access, user-written CPI-Communications programs, and user-written ICF programs .

APPC over TCP/IP

APPC over IPX

For more information about using both AnyNet and nonAnyNet sockets, see the Sockets Programming book.

Subsystems

A subsystem is a single, predefined operating environment through which the system coordinates work flow and resource usage. OS/400 can contain several that are independent operating subsystems. The run-time characteristics of a subsystem are defined in an object that is called a subsystem description. IBM supplies several subsystem descriptions that can be used with or without modification:

QINTER

Used for interactive jobs

QBATCH

Used for batch jobs

QBASE

Used for both interactive and communications batch jobs

QCMN

Used for communications batch jobs

QSERVER

File server system

QSYSWRK

Used for general system work

QUSRWRK

This is the default subsystem used for TCP/IP Client Access Host Servers that used to run in QSYSWRK.

A new subsystem can also be defined with the Create Subsystem Description (CRTSBSD) command.

Chapter 3. Optimizing communications performance 15

For more information about creating subsystems, see the Work Management book.

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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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vUsing larger sends for a given large transfer (record sizes) provides a higher application data rate and decreases CPU time. With the larger record size, the CPU has less processing to do because there are fewer application reads and writes to transfer the same amount of data.

vIf a value of *CALC is selected for maximum Systems Network Architecture (SNA) request/response unit (RU), the system selects an efficient size compatible with the frame size. The frame size is on the line description that you choose. Changing the RU size to a value other than *CALC may negate the performance feature.

vCompression with APPC should be used with caution and only for slower speed wide area network (WAN) environments. Many suggest that compression should be used with speeds 19.2 kbps and slower.

vIf you are doing tasks that include repetitive, small puts; better performance is achieved if you use ICF or CPI Communications.

See the following topics for a more complete discussion of APPC applications:

vPerformance considerations for Intersystem Communications Function

vPerformance considerations for Common Programming Interface communications

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

For more information about CICS/400, see the CICS/400 Administration and Operations Guide .

Performance considerations for intersystem communications function

You can use intersystem communications function (ICF) to write application programs that you want to communicate with advanced program-to-program communications (APPC). ICF also provides program-to-device communications between the AS/400 system and hardware devices. You must determine which system is to send data first before you write the program. ICF data management handles the communication functions and the data for your program. In particular, ICF should be used to do tasks that include repetitive, small inputs.

To optimize ICF performance, consider the following:

vEliminate unused record formats.

vUse separate record formats instead of multipurpose record formats with option indicators.

vCode to use the same record format for repeated operations.

vSet the maximum program devices equal to 1.

vUse a nonshared file.

vUse a separate indicator area.

vThe use of the ICF keywords force data and confirm should be minimized.

vUse the Request to Send keyword only when necessary.

vUse the Invite Only keyword when soliciting input from multiple devices, otherwise use the Read keyword instead.

vIf using the Invite keyword to solicit from multiple program devices, follow it with a Read-from-invited operation, not a Read operation.

To create device descriptions to get your system set up for ICF, do the following:

1.Type the appropriate Create Device Description commands on the AS/400 command line and press F4.

2.Use the online help information to choose the parameter values.

3.Press Enter. The device description is created.

For more information about ICF, see

v“Application program interface (API) performance considerations” on page 17

vICF Programming

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Performance considerations for Common Programming Interface Communications

You can use Common Programming Interface Communications (CPI Communications) to write application programs that you want to communicate with advanced program-to-communications (APPC). The interface makes use of the System Network Architecture (SNA) LU (logical unit) 6.2 architecture to do the following:

vEstablish a conversation

vSend and receive data

vExchange control information

vEnd a conversation

vNotify a partner program of errors.

Intersystem communications feature (ICF) and CPI Communications programs have similar performances for small data transfers.

To optimize CPI Communications application programs, do the following:

vMinimize the use of flush and confirm.

vReceive a compile record and parse it in your buffer.

vDo not use multiple receive calls to receive a single record.

vUse Request-to-Send only when necessary.

To add or change communications entries to get the system set up for CPI Communications, do the following:

1. Type appropriate command on the AS/400 command line and press F4.

vAdd Communications Entry (ADDCMNE)

vRemove Communications Entry (RMVCMNE)

vChange Communications Entry (CHGCMNE)

2.Use the online help information to change, add, or remove parameter values.

3.Press Enter. The communications entries are added, changed or removed.

For more information about configuring CPI Communications, see:

v“Application program interface (API) performance considerations” on page 17

vCICS/400 Administration and Operations Guide

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