Chapter 5 - Managing a 3270/SNA Service
This chapter explains how to create and manage a 3270/SNA service, and how to make the service available to users on the network. The sections that follow explain these aspects of managing a 3270/SNA service:
This chapter assumes you have read Chapter 4. If you are not familiar with the 3270/SNA features available to users, please read Chapter 1 and Chapter 2 before proceeding.
When you have installed the 3270/SNA option and gathered the required information from the mainframe computer, you can then create a 3270/SNA service on the server. Creating a 3270/SNA service has four steps:
1. Adding the service to the appropriate server and StreetTalk group.
2. Setting the station characteristics of the service.
3. Selecting the number and types of LUs on the station.
4. Specifying usage restrictions and whether or not the LUs should send TERMSELF.
To create the service, you must complete these four steps.
Note: If you press <ESC> to exit any of the screens that appear, you must begin the entire process again.
The sections that follow explain each step in detail.
Adding the Service to a Server and Group
Before adding a service, you should choose a StreetTalk group to which you can add it. For best performance, add the service to a group on the same server as the optional software and communications lines it uses.
After choosing a group, choose a name for the service that helps users identify the service. Use a name that identifies the host by model name, location, or primary function.
When you have chosen a group and a name for the service, perform these steps:
From StreetTalk Explorer
1. Click the New Service icon.
2. Enter the StreetTalk name and a description for the service, and click Next.
3. Select Server Based Service and click Next.
4. Select the server that contains the communications lines or Token-Ring card that the service will use and that will maintain the service from the drop down list and click Next.
5. Select the service type from the list, Banyan 3270/SNA Service, with the appropriate number of LUs and click Next.
6. Review the information in the Create and Start window, click the Start after creation checkbox, and click Next.
7. Click Done after StreetTalk Explorer creates and starts the service.
From the DOS Command Line
1. Run the MSERVICE program or choose the Services option from the MANAGE menu. Select the function, ADD a server-based service.
2. Enter the item name you chose for the service. Enter an appropriate description. You must be an administrator of the group.
3. In a multi-server network, select the server that contains the communications lines or Token-Ring card that the service will use. You must be an administrator of the server.
4. Select 3270/SNA as the service type.
5. Select the connection type, either SDLC or Token-Ring, which the service uses.
The Set Station Characteristics screen for the type of connection you selected appears. You use this screen to specify station characteristics of the service as a whole. The next section explains this process.
Setting Station Characteristics
Station characteristics configure the service as a whole, and require knowledge of certain mainframe-related information. If the service acts as an SDLC station, you must know which line is assigned for 3270/SNA at the server console. If your service acts as a Token-Ring station, you must know the slot number of the Token-Ring card and other configuration information that was entered when the card was configured. See Chapter 4 for details.
Setting SDLC Station Characteristics
If you have already gathered the appropriate information and filled out the worksheet in Figure 4-2, setting the SDLC station characteristics is a simple data-entry process. Figure 5-1 shows the Set SDLC Station Characteristics screen.
At the screen, proceed as follows:
1. Enter the slot and line number of the serial port you configured for 3270/SNA. You assigned this line by number during the installation process.
2. Enter the SDLC station address defined for the server. Your host system administrator or systems programmer should provide this information.
3. Enter the line type: switched or leased.
4. Enter the line speed: 1200 to 56000 baud.
5. Enter the device type of the cluster controller that your server is emulating: 3174, 3274, or 3276, as directed by the host administrator.
6. Enter the station ID (abbreviated XID) if the server will communicate with the host over a switched line.
7. Enter YES if the host uses NRZI (Non-Return-to-Zero Inverted) coding. Enter NO if the host does not use NRZI coding.
8. Enter YES if RTS should be constantly high, or NO if it should not.
9. Press <F10> to write the station characteristics to the server disk and proceed with LU-related configuration.
You can change these station characteristics at any time after you create the service. See the section, "Changing Configuration Information," for details.
When you have set the station characteristics, the system prompts you for the number of LUs in the station, as explained in the section, "Setting the Number of Logical Units."
Setting Token-Ring Station Characteristics
If you have already gathered the appropriate information and filled out the worksheet in Figure 3-2, setting the Token-Ring station characteristics is a simple data-entry process. Figure 5-2 shows the Set Token-Ring Station Characteristics screen.
At the screen, proceed as follows:
1. Enter the slot number of the Token-Ring card you installed and configured for 3270/SNA.
2. Enter the transmit buffer size in bytes: 265 to 2042.
3. Enter the LLS transmit window size: 1 to 7.
4. Enter the receive buffer size in bytes: 265 to 2042.
5. Enter the LLS receive window size: 1 to 7.
6. Enter the MAXOUT increment: 1 to 7.
7. Enter the retry count: 1 to 255.
8. Enter the response timer in seconds: 1 to 60.
9. Enter the inactivity timer in seconds: 1 to 60.
10. Enter the receiver acknowledgment timer in seconds: 1 to 60.
11. Enter the station ID (abbreviated XID): 00000 to FFFFF.
12. Enter the Token-Ring LAN address of the remote SNA host with which the service communicates in hexadecimal: 0 to FFFFFFFFFFFE.
13. Press <F10> to write the station characteristics to the server disk and proceed with LU-related configuration.
You can change these station characteristics at any time after you create the service. See the section, "Changing Configuration Information," for details.
When you have set the station characteristics, the system prompts you for the number of LUs in the station, as explained in the following section, "Setting the Number of Logical Units."
Setting the Number of Logical Units
When the system prompts you for this value, enter a number from 2 to 97, depending on the number of LUs that are defined on the host. Consult your systems programmer as needed to determine this value.
The system will prompt you for a set of LU characteristics for each LU you define here. The next section explains this process.
For each LU in the station, you must provide configuration information about its number, type, if it should send TERMSELF to the host controller, who can access it, and the locations from which it may be accessed. Figure 5-3 shows a typical Set Logical Units screen.
Note that you can use this screen at any time to add or modify an LU. For details, see the section, "Changing Configuration Information,"
To set the logical units for the service, perform these steps for each LU:
1. Enter the LU number.
2. Enter the LU type, either DISPLAY or PRINTER.
3. Enter the appropriate access rights for the LU. The access rights entry is a StreetTalk pattern, list name, or item name that controls who can access this LU. (See the section later on, "Making the Service Available to Users," for more information.) By default, all users can access the LU.
4. Accept a default of YES for issuing TERMSELF to the host when a user exits from emulation permanently, or change this field to NO.
Generally, you should accept the default. If you experience printer problems or problems with non-IBM hardware or software, you can try changing this setting. For more information on TERMSELF, see the appropriate IBM documentation.
5. Enter the appropriate LU location entries for the LU. If you want to keep the default, press <F10> to set the logical unit. You can then set another logical unit, or exit from the LU menus by pressing <ESC>. If you want to create LU location entries, press <F2>.
6. At the LU Locations menu, select ADD a location. The Available Servers menu appears. You can then proceed to create server-level, link-level, and workstation-level LU location entries, as described in the next three sections.
Repeat the appropriate steps to set all the LUs in the service. When all the LUs are properly configured, the system adds the service.
Creating a Server-level Entry
To create a server-level entry, proceed as follows:
1. At the Available Servers menu, select the server to which you want to confine access to the LU.
2. VINES prompts if you want to confine access to the LU to specific links on the server. Choose NO to make the LU available to all links on the server.
VINES returns you to the LU Locations menu, displaying the entry you just created. If you have finished, press <ESC> to return to the Set Logical Units screen. If not, you can perform other LU location access functions.
Creating a Link-level Entry
You select the link to which you want to confine access to the LU at the Available Links menu, shown in Figure 5-4.
The information on the menu is described below.
Slot-Line. The slot number combination that identifies the LAN card or asynchronous line. For LAN cards, this combination appears in the format:
slot number-0
where slot number is the number of the slot in which the LAN card is installed.
For asynchronous lines, the slot number/line number combination appears in the format:
slot number-line number
where slot number is the number of the slot in which the line's serial communications card is installed, and line number is the line's number on the card. The slot number-line number combination indicates the line's assignment.
Type. Displays the link type for each link on the menu. For LAN segments, the type of LAN card is displayed (for example, ProNET-10). For asynchronous lines, "Async" appears.
To create a link-level entry, perform the following steps:
1. At the Available Servers menu, select the server connected to the link to which you want to confine access to the LU.
2. VINES prompts if you want to confine access to the LU to specific links on the server. Choose YES.
3. The Available Links menu for the server you originally selected appears. This menu lists all the LAN segments and asynchronous lines connected to the server. Select a link to which you want to confine access to the LU.
4. VINES prompts if you want to confine access to the LU to specific workstations on the link. Choose NO to make the LU available to all workstations on the link.
The system returns you to the LU Locations menu, displaying the entry you just created.
If you have finished, press <ESC> to return to the Set Logical Units screen. If not, you can perform other LU location access functions.
Creating a Workstation-level Entry
To create a workstation-level entry, perform the following steps:
1. Select the server attached to the link on which the specific workstations reside.
2. VINES prompts if you want to confine access to the LU to specific links on the server. Choose YES.
3. The Available Links menu for the server you selected appears. This menu lists all the links connected to the server.
Select the link on which the workstations reside.
4. VINES prompts if you want to confine access to the LU to specific workstations on the link. Choose YES.
5. The Restrict LU Access to Node screen appears. Enter the address of the workstation (no more than 16 characters). The system returns you to the LU Locations menu, displaying the entry you just created.
Note that the address you enter is the link-level node address of the workstation, and can't be validated at this time. You must determine this address, and specify it only if it is relevant for the LAN type.
If you have finished, press <ESC> to return to the Set Logical Units screen. If not, you can perform other LU locations functions.
Once you have created the service and configured it to meet your needs, there are a few management tasks that you may need to perform occasionally. These tasks include:
To manage the service, you must be an administrator of the appropriate group or server. This authorization enables you to use StreetTalk Explorer or the MSERVICE or OPERATE commands to manage the service. If the service appears on the resulting screen, select it. Otherwise, search for it until it appears, and select it. The sections that follow provide general information on the management tasks listed above.
For details on performing these tasks, including generating a log report, see the Banyan Server Operations Guide.
Starting and Stopping the Service
Before you can make the service available to users, you must start it.
To make certain changes to the service, you have to stop it. These changes include:
Using another serial communications line assigned at the server console, or another Token-Ring card. Making changes to the cabling to the host computer, modems, or modem eliminators. Changing the service configuration for the station or any LUs. Caution: Be sure to notify users before you stop the service. Anyone using a host computer associated with the service is disconnected immediately.
To start or stop the service, right-click it in StreetTalk Explorer, select Properties from the shortcut menu, and click the Start or Stop button, as appropriate. Or use the MSERVICE or OPERATE commands and select the service. Choose the START Service or STOP Service function as needed.
Changing the Service Description
To insert a new one-line description for the service, right-click it in StreetTalk Explorer, select Properties from the shortcut menu, and enter a description in the Description dialog box. Or use the MSERVICE or OPERATE commands to select the service and choose the CHANGE Service Description function.
To check if the service is running, right-click it in StreetTalk Explorer, select Properties from the shortcut menu, and check the Status. Or use the MSERVICE or OPERATE commands to select the service. The service status displays on the resulting screen. You also can view service status at the server console.
Examining Who Is Using the Service
To view which users are using the service, right-click it in StreetTalk Explorer, select Properties from the shortcut menu, and select the Users tab. Or use the MSERVICE or OPERATE commands to select the service. Choose the DISPLAY Service Users function.
To move a service from one server to another, use the MSERVICE or OPERATE commands to select the service. Choose the RELOCATE Service Data function.
When you relocate the service to the target server, make sure the service's line information or Token-Ring card configuration information matches the configuration on the target server. If it doesn't, the service cannot be used until you either make the appropriate changes to the service configuration, reassign the lines at the server console, or reconfigure the Token-Ring card.
To produce a log report on service activity, use the MSERVICE or OPERATE commands to select the service. Choose the function GENERATE Log Report.
If you are an administrator of the group to which the service belongs, you can delete the service. However, if you do so, all information related to the service is lost.
You can delete LUs or information related to them without deleting the service. To do so, change the service configuration as described in the next section.
Changing Configuration Information
All of the information you provide when adding a 3270/SNA service can be changed as needed. You may need to add more LUs, delete LUs, change the characteristics of individual LUs, or change the station characteristics to conform to mainframe requirements. Your user base and mainframe systems programmer will help you determine when to make changes, and what changes to make.
The Change SNA Configuration screen enables you to reconfigure the station and its LUs. There are three ways to arrive at this screen, as follows:
Enter the following command at the DOS prompt:
SNACFG service-name
where service-name is the StreetTalk name of the SNA service you wish to reconfigure.
Enter MSERVICE from DOS or choose the Services option from the Manage menu. If need be, SEARCH for the service you wish to manage. SELECT that service. Choose the CONTROL a service function. Choose CONFIGURE Service. Enter the following command at the DOS prompt:
OPERATE server-name
where server-name is the name of the server where the desired SNA service resides. You also can type OPERATE, then choose a server.
SELECT the desired service. Choose the CONTROL a service function. Choose CONFIGURE Service.
For any changes you make to take effect, you must STOP the service, then START it again.
Figure 5-5 shows the Change SNA Configuration screen. The upper portion of the screen displays all the functions that you can choose. The lower portion of the screen lists the LUs by number, and the type of each LU.
Choose the function you wish to perform, then enter the appropriate data on the screens that the system presents. The sections that follow explain each function.
Note that you control color and other attributes on display LUs by using adapter files. See Chapter 2 for details. To use such files, you don't have to stop the service and change its configuration.
Use this function to modify station information when required by mainframe or communications line changes. It works the same as when you add a 3270/SNA service. For details, see the earlier section, "Setting Station Characteristics."
Choose this function if you want your service to use a different connection type. For example, you choose this function if you originally configured your service to use Token-Ring, but now you want the service to use SDLC.
Perform the following steps:
1. On the Change SNA Configuration screen, choose SELECT connect type.
2. Choose the connection type, either SDLC or Token-Ring.
3. Type in the appropriate configuration information.
For details on entering SDLC information, see the earlier section, "Setting SDLC Station Characteristics."
For details on entering Token-Ring information, see the earlier section, "Setting Token-Ring Station Characteristics."
Choose this function if your service needs more LUs. The system presents the Set LUs screen. Provide an unused LU number from 2 to 97.
You then can enter the LU type and access rights information, determine whether or not to send TERMSELF, and enter LU location entries, as explained in the previous section, "Setting Logical Units."
Choose this function if you need to change the type, access rights, TERMSELF flag, or LU location entries for an LU. You also choose this function to delete an LU location entry. The cursor moves to the list of LUs in the lower portion of the screen. Choose the LU you wish to change.
The system presents the Set Logical Units screen, with the LU number filled in automatically. The screen also displays the LU location entries in effect for the LU. To change the type, access rights, or TERMSELF flag, you can reset the LU as explained in the section, "Setting Logical Units."
You can modify LU location entries from the LU Locations menu. Some situations in which you might want to do this are as follows:
You previously created a server-level entry - Server 1,*,* - but now you want to confine access to the LU to just some of the links that Server 1 is on. You previously created a link-level entry - Server 2,3-0,* - but now you want to confine access to the LU to all links that Server 2 is on. You previously created a link-level entry - Server 3,3-0,* - but now you want to confine access to the LU to a single workstation on the LAN segment connected to the LAN card in slot 3 of Server 3.
To modify an LU location entry, proceed as follows:
1. Press <F2> from the Set Logical Units screen. The LU Locations menu appears.
2. Select MODIFY a location from the LU Locations menu. Then select the LU location entry you want to modify. The Available Servers menu appears.
3. Change the appropriate server-level, link-level, or workstation-level entry. The original entry is replaced by the new one.
To delete an LU location entry, proceed as follows:
1. Select DELETE a location from the LU Locations menu.
2. Select the LU location entry you want to delete.
3. VINES prompts you to confirm your decision. Select YES to delete the entry or NO to keep it as is. In either case, VINES returns you to the LU Locations menu.
Choose this function to remove an LU from the station. The cursor moves to the list of LUs. Choose the LU you wish to delete.
Making the Service Available to Users
As an administrator, you control how users access 3270/SNA services. This section provides information on the following topics:
Using the SET3270 command to set up user access through the user profile. Providing access to 3270/SNA from the VINES menus. Providing access to 3270/SNA from the DOS command line. Making 3270/SNA resident in PC memory. Supporting 3270/PCs.
Using the SET3270 Command in the User Profile
For inexperienced users or advanced users whose emulation needs are stable, use the user profile to set up 3270/SNA emulation.
You can include a default set of 3270/SNA emulation parameters in the Sample Profile of each group, and override it as needed in individual cases.
The SET3270 command performs this function. The information you provide with the command controls all user sessions started from the Select A Connection menu. This menu is accessible from the VINES Main Menu or the HOSTS command.
The syntax of the SET3270 command is as follows:
SET3270 service-name@group@org [/LU:n] [/PLU:specifier] [/PRINTER:LPTn] [/CLU:n][/CLU2:n][/CLU3:n]
[/KEYBOARD:filespec] [/ADAPTER:filespec]
When using the SET3270 command to set up multiple host sessions, you must specify the switches in the following order:
1. /LU:n.
2. Either /CLU:n or /PLU:n.
3. /CLU2:n.
4. /CLU3:n.
Otherwise, you receive only one display session.
The parameters used with the command are discussed in the paragraphs that follow. Note that the use of all LUs, both display and print, is subject to any access rights or LU location entries you set when you configured the service.
service-name@group@org is a StreetTalk name for a 3270/SNA emulation service. This parameter is required; all the rest are optional.
/LU:number is the number, from 2 to 97, of a display LU. If this LU is not in use, the system attaches it to the user's PC. If it is in use, the PC cannot act as a terminal unless you issue this command again with a different number. If you don't specify a number, the service tries to find an available LU that the user can access.
/PLU:specifier identifies the PC as a printer LU. The specifier can be a number from 2 to 97, the word NEXT, or a blank. This switch provides a print session with the host.
If you specify NEXT, the 3270/SNA service attaches to the LU that is one greater than the display LU. If you're going to use NEXT, be sure that every other LU is a printer. For example, if LU 2 is a display, then 3 should be a printer; if 4 is a display, 5 should be a printer, and so on.
If you don't specify a number or NEXT, 3270/SNA terminal emulation attaches to the next available printer LU.
/PRINTER:LPTn is the number of the printer port on the PC to be used for the print session specified by the previous switch. It can be 1, 2, or 3. This value also can be set by an adapter file.
/CLU:n, /CLU2:n, and /CLU3:n provide additional display sessions while in 3270 emulation. The optional n specifies the number of a display LU. If you omit n, the next available one is used.
If you specify the /PLU switch, you can use only two of these additional sessions. Entering emulation automatically provides one display session. Each PC can have a maximum of four total sessions: four display sessions, or three display sessions and one print session.
/KEYBOARD:filespec indicates that the keyboard definitions file, filespec, should be used in 3270 emulation. filespec is a valid DOS file specification in the user profile that names a file created by the KB3270 program. If you don't specify a keyboard file, the default mappings shown in Chapter 1 are used.
/ADAPTER:filespec indicates that the adapter file, filespec, should be used in 3270 emulation. filespec is a valid DOS file specification that names an adapter settings file created by the GA3270 program. If you don't specify an adapter file, defaults for monochrome or CGA display are used.
Below is an example of how SET3270 can appear in a user profile:
-- set up access to 3270/SNA
set3270 ibmsna@finance@corporate /lu:2 /plu:next /clu2: /printer:lpt3 /keyboard:french.kbd /adapter:ega.dat
The example lets you use display LU 2 and printer LU 3 of the service, with any available LU for an additional display session. Printed output from the printer LU goes to PC port LPT3. The file french.kbd provides keyboard definitions. The file ega.dat provides adapter attribute settings.
Note that any parameters provided by a 3270 command issued from DOS override parameters on SET3270 in the profile. Parameters omitted from the 3270 command use the values set by SET3270 in the profile.
Once you set up user access to 3270/SNA in the profile, it is easy for users to enter emulation. They can use either of these methods:
From the VINES Main Menu, choose Communications with Other Computers. From DOS, type the HOSTS command.
In either case, the Select a Connection menu appears and displays the name of the 3270/SNA service set in the user profile. To enter emulation, the user chooses the service from the menu.
For more advanced users, or those who must access more than one 3270/SNA service, VINES provides entry to emulation from the DOS command line.
The 3270 command performs this function. Its syntax is the same as the SET3270 command described in the previous section. Chapter 2 contains information about the command for users.
The only differences between the 3270 and SET3270 commands are as follows:
SET3270 in the user profile prepares the emulation environment for a user. 3270 from the DOS command line takes the user into emulation. With SET3270, you must specify a service name. With 3270, the name can be omitted if there is a SET3270 command in the profile.
Otherwise, the two commands are identical. They accept the same parameters and use them for the same functions.
If the user specifies switches and parameters on the 3270 command, those settings override those on SET3270 in the user profile. Any parameters omitted from the 3270 command are provided by the SET3270 command in the user profile, if there is one.
When using the 3270 command to set up multiple host sessions, you must specify the switches in the following order:
1. /LU:n.
2. Either /CLU:n or /PLU:n.
3. /CLU2:n.
4. /CLU3:n.
Otherwise, you receive only one display session.
Here are some examples of issuing the 3270 command from DOS:
3270
puts the user in emulation, using the service and any other settings in the user profile.
3270 ibmsna@production@manufacturing /clu
puts the user in emulation, using the specified service and any two available display LUs.
3270 /keyboard:uk.kbd /adapter:ega.dat
puts the user in emulation using the service and any LUs requested in the profile, with keyboard mappings from the file uk.kbd, and display attributes from the file ega.dat.
Making 3270/SNA Resident in the PC
3270/SNA includes some features that allow 3270 emulation to become resident in PC memory. When 3270/SNA is resident, a user can exit to DOS while holding one or more host sessions. The user can then run file transfer programs that require a resident emulation program, or perform any other tasks in the DOS environment.
The user can return to emulation in the same session with the host by using VINES menus, the 3270 command, or a special hotkey.
This section explains how to use the memory-resident features of 3270/SNA. Topics discussed include:
How the parts of 3270/SNA work in the PC. Providing held emulation sessions that are accessible from VINES menus or the 3270 command. Providing held emulation sessions that are accessible with a hotkey. Controlling how much PC memory 3270/SNA uses.
This information also appears in Chapter 2, so that advanced users can understand and use the resident features of 3270/SNA.
How the Parts of 3270/SNA Work in the PC
To provide resident 3270/SNA features to users, you must understand how the different elements of 3270/SNA work together in the PC, and how to control them.
On the PC, 3270/SNA consists of three programs that work together to provide the user with terminal emulation. They are described in the next three sections.
I3270
I3270 reads the user profile and processes any 3270 commands that the user issues. It initializes the user's emulation environment, and leaves PC memory. If you issue I3270 as a command from DOS, I3270 accepts the same switches and parameters as the 3270 command.
When using the I3270 command to set up multiple host sessions, you must specify the switches in the following order:
1. /LU:n.
2. Either /CLU:n or /PLU:n.
3. /CLU2:n.
4. /CLU3:n.
Otherwise, you receive only one display session.
R3270
R3270 supports a programmatic interface. It can be used by file transfer programs to transfer files between the host computer and the user's PC. You can make R3270 resident if you load it from DOS with the R3270 command before the PC enters emulation.
T3270
T3270 performs screen handling and other PC-related tasks during emulation. You can make T3270 resident if you explicitly load it from DOS with the /res switch.
When the user chooses a 3270/SNA service from a menu, or issues a 3270 command, all three programs run. First, a check is made to see if R3270 is already in the PC memory; if not, it is loaded. I3270 runs next, and initializes the environment as explained above. T3270 is then loaded into memory, and remains resident along with R3270 until the user exits from emulation.
Providing Held Sessions through Menus or DOS
To enable a user to enter and exit emulation from VINES menus or the 3270 command while holding sessions, you must make R3270 resident in the PC before the user enters emulation. If R3270 is not made resident, the user has no option to leave emulation and hold sessions. All 3270/SNA programs leave PC memory when the user exits from emulation.
To make R3270 resident, enter the R3270 command from the DOS prompt or from a batch file.
To leave emulation with sessions held, the user chooses that function from the Command Menu, as explained in Chapter 1. When the user chooses this option, T3270 leaves the PC memory, and the user sees the DOS prompt.
Once R3270 is resident, users do not have to log in to the host computer when they return to 3270/SNA terminal emulation. They can also use file transfer programs to transfer files between PCs and the host computer. To return to emulation, the user can use VINES menus or issue a 3270 command.
Note that the R3270 program uses space in memory that may be required by other programs. To release the program from memory, the user can use the REL3270 command only if R3270 was the last resident program loaded. If it was not, DOS may try to use the released space incorrectly-the user should reboot or turn off the PC and begin again.
Keep in mind that exiting from emulation does not release memory.
Providing Held Sessions with a Hotkey
You can make 3270/SNA resident in a way that allows users to exit from and re-enter emulation by using a hotkey. For example, if the hotkey is <Alt-Z>, the user can press <Alt-Z> while in emulation, and return immediately to the DOS prompt with sessions held. From DOS or from an application, the user can again press <Alt-Z> to return to their emulation session. No menus or other commands are required to enter or leave emulation.
To provide this feature, you must arrange for the three 3270/SNA programs to run individually at the PC, as follows:
1. First, R3270 must run to load R3270 and make it resident.
2. Next, I3270 must run. You can provide switches on the command, using the ones supported by 3270. Settings not made by I3270 are provided by the SET3270 command in the user profile, if there is one. Switches on I3270 override those on SET3270. For details, see the earlier section, "Access from the Command Line."
The default hotkey is <Alt-Z>, but you can define another hotkey. To do so, create a keyboard definitions file with the KB3270 program and change the mapping for the hotkey. Load the keyboard mapping file with the /KEYBOARD switch on the I3270 command. The section, "Customizing the PC Keyboard," in Chapter 2 provides instructions for using KB3270.
3. Finally, T3270 /res must run. This command loads the T3270 program. The /res switch makes it resident in the PC.
You can issue the three commands from DOS, or from a batch file. You must issue them in the order specified above.
Users can then press the hotkey to enter or exit from emulation. They also can use the VINES menus, holding or releasing sessions as desired. At all times, both R3270 and T3270 remain in the PC memory.
After exiting with the hotkey, users can return to emulation by pressing the hotkey from DOS, or from any application that doesn't put the screen into a graphics mode. If they press the hotkey from an application, they return to the application the next time they press the hotkey. After exiting through the VINES menus, users can re-enter emulation by issuing I3270, 3270, or from the VINES menus.
After exiting the VINES menus, issue an I3270 or 3270 command to return to emulation, or use the VINES menus to return to the program. Do not rerun a hotkey batch file or attempt to reload resident R3270 or T3270.
Note that the R3270 and T3270 programs use space in memory that may be required by other programs. To release them, the user can use the REL3270 command, but only if R3270 and T3270 were the last two resident programs loaded. If not, DOS may try to use the released space incorrectly-the user should reboot or turn off the PC and begin again. Keep in mind that exiting from emulation does not release memory.
Controlling How Much PC Memory 3270/SNA Uses
An individual PC may have memory limitations that affect how 3270/SNA operates. If you need to, you can limit the memory used by 3270/SNA.
To limit the amount of memory used by R3270, use the /NUMLUS:n switch. This switch specifies how many concurrent sessions the user can have and therefore, the bytes of memory the program can use. If you issue the R3270 command without this switch, R3270 takes up the amount of memory required for 4 LUs.
Each LU uses 5K bytes of memory. So, if you know that a user will engage in only one session at a time, and you need to free up some PC memory, you can issue this command:
R3270 /numlus:1
To use this feature, you must issue the R3270 command directly from DOS or from a batch file. It works whether you provide held sessions from a menu or with a hotkey. Note that specifying this switch limits the number of sessions that can be requested by any subsequent 3270 commands.
If users encounter problems with 3270/SNA, error messages appear on the status line. Appendix A lists all the messages, with causes and suggested corrective actions.
This section explains two special features available for 3270/PCs:
Using the Host Session Adapter Using the 3270/PC keyboard
This information appears in Chapter 1 for any users who need it.
Using the Host Session Adapter
The 3270/PC contains a Host Session Adapter that sets the display of colors and highlighting on the PC screen. You can use the GA3270 program to create a special file that provides all the functions of that adapter. These functions include underlining and reverse video. Alternatively, you can accept the default of CGA functionality.
Do not use the adapter file along with the 3270/PC Control Program; it will not work properly. For details, see the section "Using Adapter Files" in Chapter 2.
For 3270/PCs, a special keyboard driver program, 3270PCKB.COM, allows you to use the special keys on the 3270/PC keyboard. Without this program, the 3270/PC keyboard functions as a standard DOS keyboard. Do not use 3270PCKB with the 3270/PC Control Program.
3270PCKB is memory resident, and must be loaded at the DOS prompt or from a batch file before the user enters emulation. When the command is executed, the PC displays a message that the keyboard translator is installed. With 3270PCKB, a special set of keyboard mappings is in effect, as shown in Table 5-1.
| 3270/PC Key | Function |
| PF1 through PF24 | Functions as printed on the keyboard. |
| Numeric keypad keys | Does not move the cursor. To do so, keys use the other set of arrow keys. The numeric keys enter numbers. |
| Left control keys | The following keys do not work: <TEST>, <WS CTRL>, <EX SEL>, <FINISH>, CHG SC>, <IDENT>, <COPY>, <AUTO>, PULSE>, and the window sizing key on the extreme lower left. All other keys on that keypad work as listed below, or as printed on the key. |
| <RETURN> | Does not send data to the host. It issues a newline. Use the <ENTER> key to send data. |
| <HELP> | Displays the Command Menu. |
| <SHIFT/PRINT> | Performs the DOS print screen function. |
| <PRINT> | Sends a 3270 print request. |
| <JUMP> | Performs the function to switch between concurrent display sessions. |
