Chapter 3 - Installing the 3270/SNA Option
If you are responsible for installing the 3270/SNA option in a VINES network, this chapter provides the information you need. The sections that follow discuss these aspects of installing the option:
Overview of 3270/SNA components Installing the hardware Installing the software Assigning a serial communications line Configuring a Token-Ring card
After completing the tasks described in this chapter, a system administrator can add one or more 3270/SNA services to the network and make them available to users. Chapter 4 provides complete details.
Overview of 3270/SNA Components
3270/SNA consists of a software service that connects to the host computer using either a serial communications card, or a Token-Ring card and a Token-Ring LAN.
A 3270/SNA service uses a VINES server as a station that is attached to a communications controller (37x5 or 3174 1L). For technical information on the SNA requests that the service supports, see Appendix B.
For Token-Ring communications, you use one or more Token-Ring cards to connect the server to destination hosts on the Token-Ring LAN. The Token-Ring cards that are currently supported under 3270/SNA are as follows:
IBM Token-Ring Adapter IBM Token-Ring Adapter II IBM Token-Ring 16/4 Adapter
The server and hosts may reside on the same Token-Ring LAN, or they may reside on different LANs and communicate via Token-Ring bridges. Up to three 3270/SNA services can share the same Token-Ring card.
You should configure each 3270/SNA service to communicate with a different host. However, if you want multiple services to communicate with the same host simultaneously, one of the following conditions must be true:
The services share a Token-Ring card in the server, but are configured to communicate with different Token-Ring cards in the host. The services use different Token-Ring cards in the server. In this case, you can configure the services to communicate with the same or different Token-Ring cards in the host.
For serial communications, you can use a direct line to connect the server to a local host through a modem, or through a dial-out line and modem to connect to a remote host. The service does not support auto-dial modems; to reach a remote host, you must dial out manually. As part of the installation process, you must provide the appropriate line and modem or eliminator.
The total number of LUs you can configure for all the 3270/SNA services on a server depends on the number of LUs you purchase and the capacity of your server.
Some 3270/SNA options allow you to distribute the LUs among multiple services. You can distribute the LUs among these services any way you want.
Because you can allocate LUs to services in a flexible manner, reserve as many LUs as you need for all the required services to communicate with a specific host. This eliminates the need for creating multiple services to ensure that enough LUs are available for communication with a single host.
To connect to a host, the service uses the communications line or Token-Ring LAN to transmit data to and from the host. You assign the communications line to the service as part of the installation process. All user sessions through a given service share the same communications line or Token-Ring LAN.
The 3270/SNA option requires that you meet one of the following hardware requirements:
At least one port must be available on a serial communications card installed in the server. The port allows the server to use a serial line to connect with the host. Each serial line can support one 3270/SNA service. See the Serial Communications Installation Guide for details. At least one Token-Ring card must be installed in the server. Each Token-Ring card supports up to three link station.
A link station provides buffers that a 3270/SNA service requires to communicate with a host. Each link station can support one 3270/SNA service. The number of LUs that a single service can support depends on your option. See the section "Planning the Number of Logical Units" in Chapter 4 for details.
You also must install the appropriate Token-Ring or serial communications hardware. For serial communications, the service supports both half- and full-duplex synchronous modems. The maximum allowable line speed is 56000 bps for high-performance communications cards, and 19200 bps for lower-performance communications cards.
To install a Token-Ring card, follow the steps in the appropriate VINES LAN Installation Guide for the Token-Ring card you are using. That document explains how to install a Token-Ring card, and provides most (but not all) of the configuration information that you need to know. The document does not provide information on the Token-Ring card configuration parameters that are specific to 3270/SNA. These parameters are described in a later section, "Configuring a Token-Ring Card."
To install a serial communications card, follow the steps in the Serial Communications Installation Guide. That document explains how to plan for serial communications on a server, how to configure and install the card, and how to work with the serial communications ports.
The general steps for installing the hardware are as follows:
1. Determine what Token-Ring card or serial communications card and port the service will use.
2. If necessary, install and configure the Token-Ring card or serial communications card and the serial port.
3. For Token-Ring communications, record the slot number of the card. For serial communications, record the slot number and line number of the serial port.
You will need slot number and line number information later when you configure the service.
To use 3270/SNA, optional software must be running on your server. If you purchased a server with the option from Banyan®, the software is already installed.
If you are installing 3270/SNA on a server that does not have the optional software, you must install it.
The general steps for installing the optional software are as follows:
1. Go to the server. Make sure the Server Key is in place on a parallel printer port. Insert the appropriate Option Key into the Server Key.
Alternatively, be sure that you have the Software Option Code.
2. From the Operator Menu, choose Shut Down Server Software. After the software is shut down, choose Return to Operator Menu. Then, choose System Maintenance. From the System Maintenance menu, choose the function, Manage Software Options.
3. Choose the function, Install Option Key Contents or Install Option Code Options, as appropriate. When the option is installed, you see the Manage Software Options screen. All the options on the server appear, including those you just installed.
4. Remove the Option Key. Press <ESC> and return to the Operator Menu.
5. Choose Restart Services.
The software installation process is now complete.
If you need more detailed instructions, see the section, "Managing Software Options," in the Banyan Server Operations Guide.
Assigning a Communications Line
For serial line communications, the next step in the installation process is to assign the communications line that 3270/SNA will use to communicate with the host. You must assign one line for each service that you put on the server.
To assign a line, perform these steps:
1. From the Operator Menu at the server console, choose Manage Communications.
2. From the next menu, choose Serial Communications.
3. From the next menu, choose Manage Lines.
4. Choose Assign 3270/SNA.
5. Enter the following information about the serial communications line you are using:
- The slot number of the serial communications card that is connected to the line.
- The line number.
Keep a record of this information. You need it later to configure the service.
When you have finished the steps above, a communications line is reserved for use by 3270/SNA. The installation process is complete on the server side.
You now can attach the line from the server to a modem or modem eliminator. Make sure that the line is connected to the proper hardware on the host side.
Before adding a service to the network and making it available to users, you must gather information about the host mainframe so that you can configure the service properly. Chapter 4 lists all the information required. Repeat the steps in Chapter 4 for each service you create.
For Token-Ring communications, you must specify several configuration parameters that are specific to using the 3270/SNA option with Token-Ring cards. Do not confuse these parameters with the 3270/SNA service parameters that you enter when you create the 3270/SNA service. You enter card parameters at the server console when you configure the Token-Ring card.
The card parameters are as follows:
Maximum packet size Number of transmit buffers Number of link stations Link address
These parameters are described in the next five sections. The section, "Token-Ring Station Worksheet," provides a worksheet for recording the Token-Ring card configuration parameters. The section, "Specifying Token-Ring Card Parameters," describes how to enter these parameters in the Token-Ring card configuration.
The maximum packet size is the length of the transmit buffer in bytes. The transmit buffer is an area in memory that the Token-Ring card uses to format Token-Ring packets for transmission to the host. A Token-Ring packet contains a variable amount of user data and control information.
In general, valid maximum packet sizes for the Token-Ring card range from 1520 to 8192 bytes. However, the largest maximum packet size value you can specify depends on the type of Token-Ring card and the data rate that the card supports. Table 3-1 lists the largest maximum packet size values for each Token-Ring card.
| Card Type | Data Rate | Maximum Packet Size |
| IBM Token-Ring Adapter | 4 Mbps | 2048 bytes |
| IBM Token-Ring Adapter II | 4 Mbps | 2048 bytes |
| IBM Token-Ring 16/4 Adapter | 4 Mbps | 4464 bytes |
| 16 Mbps | 8192 bytes |
Keep in mind that the value you specify includes 6 bytes of overhead in Token-Ring packets.
The default maximum packet size is 1520. The value you specify must be a multiple of eight, beginning with 1520. For example, you could specify 1520, 1528, or 1536 and so on, up to 8192.
The maximum packet size value in the card configuration provides a common resource for all communications software that uses the card, such as all 3270/SNA services on the server, VINES, and TCP/IP. The smallest value that you can enter for the maximum packet size (1520) is large enough to handle non-3270/SNA Token-Ring packets.
The value you enter for maximum packet size sets an upper limit on the transmit buffer size that you configure later for each 3270/SNA service that uses the card. This service configuration value specifies the maximum size of the packet that the service can send to the host with which it communicates.
Since up to three services can use a card and each service should communicate with a different host, all the services that use a card can have different transmit buffer size values. Before you configure the maximum packet size for the card, identify the service that requires the largest transmit buffer size in its configuration. The card's maximum packet size must be greater than or equal to this service's transmit buffer size requirements. For details, see "Planning Token-Ring Characteristics" in Chapter 4.
For example, you want two 3270/SNA services to share a card. The service that sends the largest packets requires a transmit buffer size of 1600. The other service requires a transmit buffer size of 1560. You must specify a maximum packet size of at least 1600 when you configure the card. When you configure the two services, you specify transmit buffer sizes of 1600 and 1560 respectively.
To identify the service that requires the largest transmit buffer size, consult with the mainframe administrator or systems programmer responsible for the host with which the service communicates. The receive buffer size in the NCP configuration on this host must be either greater than or equal to the transmit buffer size for the service. The receive buffer size is the maximum length (in bytes) of the receive buffer, which is an area in memory used for receiving Token-Ring packets.
When you configure the transmit buffer size for the Token-Ring card, you should also take into account the size of Token-Ring packets containing VINES data. Remember that your server uses the Token-Ring LAN for both VINES and SNA communication.
The number of transmit buffers that the Token-Ring card uses for communication ranges from one to eight. A value of one is recommended. Other values may be appropriate depending on network conditions.
Each 3270/SNA service requires one link station. You can have up to three link stations per Token-Ring card. The number of link stations that you specify should equal the number of 3270/SNA services that will use the Token-Ring card to communicate with hosts.
Figure 3-1 shows a server with two Token-Ring cards that connect the server to two Token-Ring LANs, LAN1 and LAN2. The server communicates with two IBM hosts on LAN1, and with one IBM host on LAN2. To communicate with the hosts, one 3270/SNA service is created for each of the three hosts - cics@sna@corp, tso@sna@corp and db@sna@corp. Two link stations are configured for the Token-Ring card that connects the server to LAN1 and one link station for the Token-Ring card that connects the server to LAN2.
You must configure each 3270/SNA service to use the appropriate Token-Ring card. You do this by specifying the card's slot number in the service configuration. For example, you must specify slot number 4 when you configure cics@sna@corp. See Chapter 4 for details on planning 3270/SNA service configurations.
Link Address is the Token-Ring LAN address of the Token-Ring card. Valid settings range from 0 to FFFFFFFFFFFE (hexadecimal).
Each Token-Ring LAN card has a default link address. Consult your mainframe administrators or systems programmers to determine whether the default is acceptable. Use the default unless the administrators or programmers tell you otherwise.
The administrators or programmers might ask you to override the default in certain situations. For example, if 3270/SNA services use the card to communicate with hosts through IBM 372x controllers, you must use telephone dial numbers (0 through 9) to enter the card's link address. You must specify the address in the following format:
4000 XYYY YYYY
where X can be a number from 0 through 7 and YYY YYYY can consist of numbers from 0 through 9.
The 372x controllers were originally designed to communicate with other nodes over telephone lines only, and require link addresses to use dial numbers. These controllers require a special upgrade to be compatible with Token-Ring LANs.
Figure 3-2 is a worksheet for setting up the configurations of Token-Ring cards and the 3270/SNA services that use them. It helps you to configure the card at the server console, and helps you later when you set up the configurations of the services that use the card. At this time, record the information you need to configure the Token-Ring card. Later, record the necessary information to configure each 3270/SNA service that uses the card (see Chapter 4 for details). Make as many copies of the worksheet as you need to record service information.
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Specifying Token-Ring Card Parameters
Before you specify Token-Ring card parameters, make sure that you have the Token-Ring Station Worksheet that you filled out handy. You might also need the VINES LAN Installation Guide for the Token-Ring card.
To specify Token-Ring card parameters, perform the following steps:
1. From the Operator Menu at the server console, choose System Maintenance. From the next menu, choose Configure/Diagnose Server. Then, choose Add Cards/Change Card Configuration.
2. From the Add/Change Card Screen, choose CHANGE card settings. Then select the Token-Ring card to be used for SNA communication.
3. At the Change Card Settings screen, enter the appropriate maximum packet size, number of transmit buffers, number of link stations, and link address settings.
4. Reboot the server to put your changes into effect.
