OpenVMS System Manager's Manual

Updated: 11 December 1998

OpenVMS System Manager's Manual

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24.4 Understanding the LATCP Utility

The LAT Control Program (LATCP) utility configures and controls the LAT software on OpenVMS systems. LATCP commands let you stop and start the LAT driver (which implements the LAT protocol) and modify or display LAT characteristics of the OpenVMS node.

With LATCP, you can set up your system as a service node, which offers one or more resources (services) for access by users on other systems in the local area network (LAN).

You can also use LATCP to set up the system to allow its users to access services on other systems in the LAN. In this case, the system can act like a terminal server: it can manage multiple user sessions simultaneously for connections to services on other nodes.

You can use LATCP to set up your system to support incoming access only, outgoing access only, or both incoming and outgoing access. You can also set up your system so that it supports neither incoming nor outgoing access.

When you set up your system to support outgoing access, the LAT software manages a database of LAT services and nodes. The software builds the database when you enable outgoing access on your node. The software begins to collect LAT service announcements---multicast messages sent by LAT service nodes---and builds the database based on these service announcements. You can use LATCP to display the services and nodes in this database and to control the size of the database. Allow outgoing access on systems that can tolerate the additional overhead, such as standalone systems.

Use LATCP to perform the following actions:

Specify operational characteristics for your node and its services
Turn the state of the LAT port driver (LTDRIVER) on and off
Display the status of LAT services and service nodes in the network
Display the status of links created on your LAT node
Display the status of your LAT node
Show and zero LAT counters
Create, delete, and manage LAT ports
Recall previously entered LATCP commands so that you can execute them again without having to reenter them
Create subprocesses so that you can execute DCL commands without exiting from LATCP

With the LAT protocol, you can set up LAT application ports on the local node so that users can access printers and other asynchronous devices that are connected to LAT terminal servers or service nodes on the LAN. The remote devices must be configured appropriately.

24.4.1 Invoking and Exiting LATCP

Enter the following command to invoke LATCP:

$ RUN SYS$SYSTEM:LATCP LATCP>

At the LATCP> prompt, you can enter LATCP commands. To exit LATCP, enter EXIT or press Ctrl/Z at the LATCP> prompt.

You can also execute a single LATCP command by using a DCL string assignment statement, as shown in the following example:

$ LCP :== $LATCP $ LCP SET NODE/STATE=ON

LATCP executes the SET NODE command and returns control to DCL.

24.4.2 LATCP Commands

Table 24-1 summarizes the LATCP commands.

Table 24-1 LATCP Commands
Command Function

ATTACH Transfers control from your current process to the specified process.

CREATE LINK Creates LAT data links.

CREATE PORT Creates a logical port on the local node.

CREATE SERVICE Creates a service on a service node.

DEFINE/KEY Assigns a command string to a function key on your keypad.

DELETE LINK Deletes a LAT data link from a node.

DELETE PORT Deletes an application port or dedicated port.

DELETE QUEUE_ENTRY Deletes an incoming queued request from the local node.

DELETE SERVICE Deletes a service on a service node.

EXIT Returns the user to DCL command level.

HELP Displays help text for LATCP commands.

RECALL Recalls LATCP commands that you entered previously so that you can execute them again.

REFRESH Refreshes your display screen, for example, after your display has been overwritten by output from some other source.

SCROLL Allows you to retrieve information that has scrolled off the screen.

SET LINK Modifies characteristics of LAT data links.

SET NODE Specifies LAT characteristics for a node.

SET PORT Maps a logical port on a node to either a remote device on a terminal server or a special application service on a remote LAT service node.

SET SERVICE Changes service characteristics.

SHOW LINK Displays the characteristics of links on your node.

SHOW NODE Displays the characteristics of nodes.

SHOW PORT Displays port characteristics.

SHOW QUEUE_ENTRY Displays information about requests, or entries, queued on the local node.

SHOW SERVICE Displays characteristics of LAT services known to your node.

SPAWN Creates a subprocess.

ZERO COUNTERS Resets the node counters, service counters, and link counters maintained by your node.

**Table 24-1 LATCP Commands**
Command	Function
ATTACH	Transfers control from your current process to the specified process.
CREATE LINK	Creates LAT data links.
CREATE PORT	Creates a logical port on the local node.
CREATE SERVICE	Creates a service on a service node.
DEFINE/KEY	Assigns a command string to a function key on your keypad.
DELETE LINK	Deletes a LAT data link from a node.
DELETE PORT	Deletes an application port or dedicated port.
DELETE QUEUE_ENTRY	Deletes an incoming queued request from the local node.
DELETE SERVICE	Deletes a service on a service node.
EXIT	Returns the user to DCL command level.
HELP	Displays help text for LATCP commands.
RECALL	Recalls LATCP commands that you entered previously so that you can execute them again.
REFRESH	Refreshes your display screen, for example, after your display has been overwritten by output from some other source.
SCROLL	Allows you to retrieve information that has scrolled off the screen.
SET LINK	Modifies characteristics of LAT data links.
SET NODE	Specifies LAT characteristics for a node.
SET PORT	Maps a logical port on a node to either a remote device on a terminal server or a special application service on a remote LAT service node.
SET SERVICE	Changes service characteristics.
SHOW LINK	Displays the characteristics of links on your node.
SHOW NODE	Displays the characteristics of nodes.
SHOW PORT	Displays port characteristics.
SHOW QUEUE_ENTRY	Displays information about requests, or entries, queued on the local node.
SHOW SERVICE	Displays characteristics of LAT services known to your node.
SPAWN	Creates a subprocess.
ZERO COUNTERS	Resets the node counters, service counters, and link counters maintained by your node.

For detailed information about LATCP commands and qualifiers, refer to the OpenVMS System Management Utilities Reference Manual.

24.5 Starting Up the LAT Protocol

As system manager, you start up the LAT protocol and configure your node as a service node by executing the command procedure SYS$STARTUP:LAT$STARTUP. This procedure executes the following two procedures:

LAT$CONFIG.COM, to load the LAT terminal driver LTDRIVER and create the LATACP process
LAT$SYSTARTUP.COM, to execute LATCP commands that define LAT characteristics

How to Perform This Task

To make sure the LAT protocol is started each time the system boots, add a command to execute this procedure in the general-purpose, site-specific startup command procedure, described as follows. (See Section 5.2.1 for more detailed information about this command procedure, including the file specification used to identify it in your operating system.)

To set up your node as a LAT service node and start the LAT protocol software on your system each time the system boots, edit the general-purpose, site-specific startup command procedure to add the following line:

$ @SYS$STARTUP:LAT$STARTUP.COM

When the general-purpose, site-specific startup command procedure executes this command, it invokes LAT$STARTUP.COM, which in turn invokes the LAT$CONFIG and LAT$SYSTARTUP command procedures.

You can append any of the following arguments to the command line that invokes LAT$STARTUP to specify unique LAT characteristics for your node. The procedure will pass these arguments to LAT$SYSTARTUP.COM to define the LAT characteristics you specify.

$ @SYS$STARTUP:LAT$STARTUP "P1" "P2" "P3" "P4" "P5"

Compaq recommends that you modify LAT$SYSTARTUP.COM directly, rather than passing parameters in P1 through P5. However, if you choose to use P1 through P5, the arguments have the following meanings:

Argument Format Meaning

P1 Service-name Name of the service. For clustered service nodes, use the cluster alias as the service name. For independent service nodes, use the DECnet node name. LAT$SYSTARTUP.COM uses the argument P1 to assign a service name to the node (with the LATCP CREATE SERVICE command).

P2--P4 Any of the following names: LAT$SYSTARTUP.COM uses the arguments to assign LAT node characteristics (with the LATCP SET NODE command).

/IDENTIFICATION= "string" Description of the node and its services that is advertised over the local area network (LAN). The default is the string defined by the logical name SYS$ANNOUNCE. Make sure you include five sets of quotation marks around the identification string. For example:
"/IDENTIFICATION=" - """""Official system center"""""

/GROUPS=(ENABLE= group-list) Terminal server groups qualified to establish connections with the service node. By default, group 0 is enabled.

/GROUPS=(DISABLE= group-list) Removes previously enabled terminal server groups. If you are specifying the preceding qualifier to enable groups, you can combine the qualifiers into one, as shown in the example that follows this table.

P5 Any qualifiers valid with the CREATE SERVICE command LAT$SYSTARTUP.COM uses this argument to assign service characteristics with the LATCP CREATE SERVICE command. You can specify the /IDENTIFICATION, /LOG, and /STATIC_RATING qualifiers. Specify several qualifiers as shown in the following example:
"/IDENTIFICATION=" -
"""""Official system node""""" -
/STATIC_RATING=250"

Argument	Format	Meaning
P1	Service-name	Name of the service. For clustered service nodes, use the cluster alias as the service name. For independent service nodes, use the DECnet node name. LAT$SYSTARTUP.COM uses the argument P1 to assign a service name to the node (with the LATCP CREATE SERVICE command).
P2--P4	Any of the following names:	LAT$SYSTARTUP.COM uses the arguments to assign LAT node characteristics (with the LATCP SET NODE command).
	/IDENTIFICATION= "string"	Description of the node and its services that is advertised over the local area network (LAN). The default is the string defined by the logical name SYS$ANNOUNCE. Make sure you include five sets of quotation marks around the identification string. For example: "/IDENTIFICATION=" - """""Official system center"""""
	/GROUPS=(ENABLE= group-list)	Terminal server groups qualified to establish connections with the service node. By default, group 0 is enabled.
	/GROUPS=(DISABLE= group-list)	Removes previously enabled terminal server groups. If you are specifying the preceding qualifier to enable groups, you can combine the qualifiers into one, as shown in the example that follows this table.
P5	Any qualifiers valid with the CREATE SERVICE command	LAT$SYSTARTUP.COM uses this argument to assign service characteristics with the LATCP CREATE SERVICE command. You can specify the /IDENTIFICATION, /LOG, and /STATIC_RATING qualifiers. Specify several qualifiers as shown in the following example: "/IDENTIFICATION=" - """""Official system node""""" - /STATIC_RATING=250"

Note that if you want to do any of the following LAT network tasks, you must edit LAT$SYSTARTUP.COM (described in Section 24.6):

Set up LAT printers.
Create special application services.
Set up the node to allow outgoing connections (to support the SET HOST/LAT command).

For a full description of LATCP commands and qualifiers, refer to the OpenVMS System Management Utilities Reference Manual.

Example

The following command creates the service OFFICE on the service node MOE, which is part of the OFFICE cluster (refer to Figure 24-1):

$ @SYS$STARTUP:LAT$STARTUP OFFICE

24.6 Customizing LAT Characteristics

To define special LAT characteristics for your node, edit the site-specific command procedure SYS$MANAGER:LAT$SYSTARTUP.COM. This command procedure contains LATCP commands that define LAT characteristics. LAT$SYSTARTUP.COM is invoked when you execute the LAT$STARTUP command procedure. As explained in Section 24.5, you typically execute LAT$STARTUP.COM from the general-purpose, site-specific startup command procedure.

If you want your node to be a LAT service node that only supports incoming connections from interactive terminals, editing LAT$SYSTARTUP.COM is not necessary. You can assign a service name and other characteristics by specifying parameters when you invoke the command procedure SYS$STARTUP:LAT$STARTUP, as described in Section 24.5.

However, you can edit LAT$SYSTARTUP.COM to add LATCP commands that customize LAT characteristics for your node, for example:

Task For More Information

Create more than one service Section 24.6.1

Create logical ports for special application services and printers Section 24.6.2

Enable queued incoming requests Section 24.6.3

Enable outgoing LAT connections to support the SET HOST/LAT command Section 24.6.4

Tailor node characteristics ¹ Section 24.6.5

Task	For More Information
Create more than one service	Section 24.6.1
Create logical ports for special application services and printers	Section 24.6.2
Enable queued incoming requests	Section 24.6.3
Enable outgoing LAT connections to support the SET HOST/LAT command	Section 24.6.4
Tailor node characteristics ¹	Section 24.6.5

¹For example, to assign special service announcements or LAN links (using the SET NODE and SET LINK commands).

Caution

Do not edit the command procedures LAT$STARTUP.COM and LAT$CONFIG.COM. These are procedures supplied by Compaq to perform functions necessary for the LAT protocol to run correctly. Edit only LAT$SYSTARTUP.COM to define LAT characteristics specific to your site.

If you edit LAT$SYSTARTUP.COM, you should add only LATCP commands. In addition, you should conform to the order of commands in the template file SYS$MANAGER:LAT$SYSTARTUP.TEMPLATE. Section 24.6.5 provides a sample edited LAT$SYSTARTUP procedure. The OpenVMS System Management Utilities Reference Manual contains full descriptions of all the LATCP commands you can include in LAT$SYSTARTUP.COM.

24.6.1 Creating Additional Services

The LAT$SYSTARTUP.COM procedure provided by Compaq creates one service. This can be a primary service, one through which users can access the general computing environment. It can also be a special application service, such as a data entry program or an online news service.

You can also create a limited service with a fixed number of LTA devices, as described in Section 24.6.2.3.

The LAT$SYSTARTUP.COM procedure creates the service with the same name as that of your node, unless you specify a unique service name as an argument to the @SYS$STARTUP:LAT$STARTUP.COM command, as explained in Section 24.5.

How to Perform This Task

To create services in addition to the one provided in LAT$SYSTARTUP.COM, use the CREATE SERVICE commands, which you can add to LAT$SYSTARTUP.COM. Note that if you create an application service, Compaq recommends that you assign the name of the application program. For more information about the LATCP command CREATE SERVICE, refer to the OpenVMS System Management Utilities Reference Manual.

Example

The following example creates the application service NEWS on the local node:

$ LCP :== $LATCP $ LCP CREATE SERVICE /APPLICATION NEWS

24.6.2 Setting Up Ports

The LAT$SYSTARTUP.COM file provided by Compaq includes sample commands to create logical ports on the service node and associates them with physical ports or services on the terminal server node. These ports can be used for application services and remote printers.

How to Perform This Task

To create ports, enable the sample commands by removing the exclamation points (!) that precede them in the LAT$SYSTARTUP.COM file, or add similar CREATE PORT and SET PORT commands to that file to meet your needs. For information about the LATCP commands CREATE PORT and SET PORT, refer to the OpenVMS System Management Utilities Reference Manual.

Note

Compaq strongly recommends that you create application ports and dedicated ports after the LATCP command SET NODE/STATE=ON is executed. This minimizes nonpaged pool memory usage and eliminates the possibility of creating duplicate ports.

Note that you may encounter the following error when attempting to create an application port (with a command such as LCP CREATE PORT LTA5001:/APPLICATION, for example):

%LAT-W-CMDERROR, error reported by command executor -SYSTEM-F-DUPLNAM, duplicate name

This error indicates that the LAT application port you are trying to create is already created by some other application. This application could be LATCP itself (LATCP's port, LATCP$MGMT_PORT, is used to communicate with LTDRIVER).

To avoid this error, make sure the SET NODE/STATE=ON command is executed before any commands that create application ports or dedicated ports. You can also use the LATCP command SET NODE/DEVICE_SEED. For more information about the SET NODE/DEVICE_SEED command, refer to the OpenVMS System Management Utilities Reference Manual.

24.6.2.1 Setting Up Printers

If you set up a port for a printer, you must also perform the following tasks:

Create a spooled output queue for the printer.
Add a command to start the queue to the startup command procedure that starts your queues, or to the general-purpose, site-specific startup command procedure.

These tasks are described in Chapter 13.

24.6.2.2 Setting Up Special Application Services

To establish a special application service, include the /DEDICATED qualifier when defining a LAT port. The application program to which the service connects must define the same dedicated port. For example, the following commands set up ports for an application service called NEWS:

$ LCP :== $LATCP $ LCP CREATE PORT LTA333:/DEDICATED $ LCP SET PORT LTA333:/SERVICE=NEWS

Before application services can be available to user terminals on the LAT network, you must start the application program. You usually add commands to SYLOGIN.COM to do this.

24.6.2.3 Setting Up Limited Services

Application services with dedicated ports allow you to create a predetermined number of LTA devices (LAT terminals, for example) that are under the control of a process supplied by the system. In that environment, however, the user cannot log in to the service because no way exists for dedicated LTA devices to run the system login image (LOGINOUT.EXE).

You can create a limited service that allows users to log in to a predetermined number of LTA devices associated with that limited service. When all those devices are in use, the LAT software will reject additional connection requests to that service, as indicated by "service in use" error messages. Creating a limited service in this way allows you to control the number of LAT users on your system. (Note, however, that you cannot control which LTA device will be assigned when a user connects to the limited service.)

The following example sets up a limited service with two predetermined LTA devices:

$ LCP :== $LATCP $ LCP CREATE SERVICE /LIMITED RESTRICTED $ LCP CREATE PORT LTA100 /LIMITED $ LCP CREATE PORT LTA101 /LIMITED $ LCP SET PORT LTA100 /SERVICE=RESTRICTED $ LCP SET PORT LTA101 /SERVICE=RESTRICTED

When a user attempts to connect to the limited service named RESTRICTED, the LAT software will choose either LTA100 or LTA101 (whichever is available first) and complete the user connection. The user can then log in to that system. If another user connects to the service, that second connection attempt will be assigned to the remaining LTA device. The user can then log in to that second system. When the two devices associated with the limited service named RESTRICTED are both in use, any subsequent attempts to connect to that service will be rejected, as indicated by the "service in use" error message.

When a user logs out of the system (LTA100 or LTA101), that LTA device is not deleted. Instead, it is reset to accept the next connection request to the limited service.

24.6.3 Queuing Incoming Requests

By default, incoming requests to limited or application services are queued. This means that if you attempt to connect to a limited or application service (by using a terminal server port with forward queuing enabled or by entering the DCL command SET HOST/LAT/QUEUE), the LAT software will queue, rather than reject, this connection request if the service has no available ports.

How to Perform This Task

You can set up and manage a service that queues incoming connect requests as follows:

Use the LATCP command SHOW SERVICE to determine whether the service has queuing enabled or disabled.
If queuing is disabled, use the SET SERVICE /QUEUED command to enable queuing.
Use the SET NODE /QUEUE_LIMIT=n command on the local node to control the number of free queue slots (where n is between 0 and 200).
Use the SHOW QUEUE_ENTRY [queue-entry-id] command to view entries in the local queue.
Use the DELETE QUEUE_ENTRY [queue-entry-id] command to delete an entry from the local queue.

Refer to the OpenVMS System Management Utilities Reference Manual for more detailed descriptions of the LATCP commands and qualifiers you use to support queued requests.

Example

The following example shows how to enable queuing on your system:

$ LCP :== $LATCP $ LCP SET SERVICE /QUEUE

Note

If a system is configured to handle queued connect requests, that system must be set up as follows to avoid possible queue connection failures:

Incoming and outgoing connections must be enabled.
User group codes and service group codes must be identical.

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