Document revision date: 19 July 1999
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OpenVMS System Management Utilities Reference Manual
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RECALL

Displays previously entered LATCP commands on the screen so that you can execute them again.

Format

RECALL [command-specifier]

Parameter

command-specifier

Specifies the number or the first several characters of the LATCP command you want to recall. Command numbers can range from 1 to 20. The most recently entered command is number 1.

Use the /ALL qualifier to display all the commands in the RECALL buffer, along with their command number so that you can determine the number of the command that you want to recall.

If you do not include the command specifier or the /ALL qualifier when entering the RECALL command, LATCP displays the last command.

Qualifiers

/ALL

Specifies that LATCP display all the commands in the RECALL buffer. LATCP displays the number of each command.

Description

When you enter a LATCP command, LATCP stores it in a RECALL buffer for later use with the RECALL command. The RECALL command itself is never stored in the RECALL buffer.

When you use the RECALL command, LATCP displays the recalled command but does not process it. If you want the command processed as it appears, press Return. You can use the command line editing facility to make minor changes in the command line and then press Return to process the revised version of the command.

Examples

#1 

LATCP> RECALL 2

This command recalls the second-to-last command you entered.

#2 

LATCP> RECALL SET

This command recalls the last SET command you entered.

REFRESH

Refreshes the display screen so that any output from some other source (such as a broadcast message) is erased from the screen.

Format

REFRESH

Parameters

None.

Description

Use the REFRESH command to refresh your display screen after output from other sources has overwritten the display screen. For example, if a broadcast message from a terminal server user is displayed on your screen, use the REFRESH screen to erase the broadcast message from the display. By default, you can refresh your screen by pressing Ctrl/W at the LATCP prompt.

Example


LATCP> REFRESH

This command refreshes the display on your screen.

SCROLL

Retrieves information that has scrolled off the screen, either up or down.

Format

SCROLL

Parameters

None.

Qualifiers

/DOWN[=value]

Scrolls the LATCP screen display down the number of lines indicated by the specified value. For convenience, you can also use the Next (or Next Screen) key on your keyboard to scroll down 15 lines (instead of entering the SCROLL/DOWN=15 command).

If you do not specify a value, the default value is 1.

/UP[=value]

Scrolls the LATCP screen display up the number of lines indicated by the specified value. For convenience, you can also use the Prev (or Prev Screen) key on your keyboard to scroll up 15 lines (instead of entering the SCROLL/UP=15 command).

If you do not specify a value, the default value is 1.

Description

The SCROLL command allows you to retrieve information that has scrolled off the screen (either up or down). The command works only after a LATCP SHOW command has produced output that scrolled off the screen display area. Each subsequent SHOW command erases the previous output area such that the SCROLL command retrieves the screen display produced by the last executed SHOW command.

Example


LATCP> SCROLL /UP=5

This command scrolls up to view five lines of screen display that has previously scrolled off the viewing area.

SET LINK

Changes the characteristics of LAT data links. You must have OPER privilege to use this command.

Format

SET LINK link-name

Parameter

link-name

Specifies the name for a LAT data link. A link name can have up to 16 ASCII characters. The characters allowed are as follows:

The SHOW LINK command displays the names of the links defined for a node.

Qualifiers

/LOG

/NOLOG (default)

Specifies whether LATCP displays a message confirming that the link's characteristics were modified. If you do not specify the /LOG or /NOLOG qualifier, the default is that no message will be displayed.

/STATE=option

Specifies availability of the link for use. The two options for STATE are:
ON Specifies that the link will be available for use with the LAT protocol running.
OFF Specifies that the link will not be available for use.

If you do not specify the /STATE=option qualifier, the default is that the link will be available (ON).

Description

The SET LINK command changes the characteristics for a LAT data link, which must have been created previously in one of the following ways:

Example


LATCP> SET LINK NETWORK_A /LOG /STATE=ON

This command directs LATCP to start the controller for link NETWORK_A and then to display a confirmation message.

SET NODE

Specifies the LAT characteristics of your local node. You must have OPER privilege to use this command.

Format

SET NODE [node-name]

Parameter

node-name

Specifies a node name for your local node. By default, the node name is the translation of SYS$NODE. A LAT node name should be the same as the DECnet node name. If the node is not running DECnet but will be in the future, Compaq recommends that you define SYS$NODE and use it for both DECnet and LAT node names.

A LAT node name can be from 1 to 16 ASCII characters. The characters allowed are as follows:

Qualifiers

/ANNOUNCEMENTS

/NOANNOUNCEMENTS

Controls whether your OpenVMS system multicasts information to the network.

If you specify /NOANNOUNCEMENTS, LAT service announcements are disabled on the local node. Remote nodes must rely on the LAT service responder feature in the LAT protocol Version 5.2 or higher to connect to the local node. Therefore, Compaq recommends that you use this qualifier only in a networking environment where newer model terminal servers and hosts are present (all LAT hosts, terminal servers, and PCs are running LAT protocol Version 5.2 or higher).

If you specify /NOANNOUNCEMENTS in an environment where LAT protocol Version 5.1 is present, those LAT protocol Version 5.1 systems (for example, DECserver 100, 200, and 500 systems) will be unable to connect to any of the systems that have LAT service announcements disabled.

/CIRCUIT_TIMER[=msecs]

Controls the interval in milliseconds (msecs) between messages sent from the local node to other service nodes or terminal servers while connections to those nodes are active. Use this qualifier only if your node allows outgoing connections (/CONNECTIONS=OUTGOING_ONLY or /CONNECTIONS=BOTH).

A low value for the interval decreases the response time for the port but increases the demand on service nodes. Set the circuit timer in the range of 10 to 1000 msecs.

The default value of 80 msecs gives a generally acceptable response time while creating a moderately low overhead on the service nodes. You cannot change this parameter when active or pending LAT connections exist.

/CONNECTIONS=option

Specifies the type of connections permissible on the local node. The four options for CONNECTIONS are:
INCOMING_ONLY Specifies that the local node permit incoming connections only.
OUTGOING_ONLY Specifies that the local node permit outgoing connections only. Specify this on systems that can tolerate the overhead associated with outgoing connections, such as standalone systems.
BOTH Specifies that the local node permit both incoming and outgoing connections. Specify this on systems that can tolerate the overhead associated with outgoing connections, such as standalone systems.
NONE Specifies that the local node disallow both incoming and outgoing connections.

If you do not specify the /CONNECTIONS=option qualifier, the default is that the node will permit incoming connections only.

/CPU_RATING=cpu-power

/NOCPU_RATING

The /CPU_RATING qualifier assigns your local node a rating that represents the power of your node's CPU (central processing unit) relative to other CPUs in the LAN. The value of cpu-power can range from 1 (for a CPU with the lowest power) to 100 (for a CPU with the highest power).

When a terminal server or node requests a connection to a service that is offered on the local node and one or more other service nodes, the requesting node selects the service node with the highest (most favorable) service rating, based on the overall level of activity of the node that offers the service and the amount of memory. This selection process is called load balancing.

You can influence the rating for services on your node by specifying a value for the /CPU_RATING qualifier. If you specify a high value for cpu-power, the LAT driver will calculate a relatively high service rating for services on your node (service ratings as high as 255 are possible). If you specify a low value, the LAT driver will calculate relatively low service ratings; connections will most likely be made to the same service that is offered on other nodes. In either case, the LAT driver can calculate a greater range of values for dynamic service ratings (the entire range from 0 to 255). Consequently, the ratings will more accurately reflect the availability of the service node.

If you do not specify either the /CPU_RATING=cpu-power or /NOCPU_RATING qualifier, the default is that no CPU rating will be used A value of 0 indicates no CPU rating.

/DEVICE_SEED[=value]

Sets the default starting number (within a range from 1 to 9999) for the unit numbers that will be assigned to new LTA devices. Note that when ports are created by assigning a channel to LTA0: with the $ASSIGN system service, the channel numbers fall in this same range.

The default device seed value is approximately half of the maximum unit number (which you set by using the /UNIT_NUMBER_MAXIMUM qualifier). Interactive LAT ports, and those created with the CREATE PORT/LOGICAL command, are assigned unit numbers beginning with the specified device seed value and continuing up to the maximum unit number. When the maximum unit number is reached, the port is assigned the next available unit number beginning at the bottom of the range (LTA1:).

Note that each time you specify the /UNIT_NUMBER_MAXIMUM qualifier, the device seed value is reset to approximately half of the newly specified maximum unit number.

/FORWARD_SESSION_LIMIT[=value]

Controls the number of sessions (a value within a range from 16 to 255) allowed on each outgoing connection. By default, 16 sessions are allowed on an outgoing connection, which means that 16 individual processes can direct the DCL command SET HOST/LAT to the same remote node.

You must increase the value for the /FORWARD_SESSION_LIMIT qualifier if a user on your system enters the command SET HOST/LAT and receives an error message indicating that the session limit for the LAT circuit has been reached (%LAT-F-VCSESLIM). Note, however, that you can change this value only when no connections exist.

/GROUPS=option[,...]

Gives the listed groups access to services offered on your local node or prevents the listed groups from accessing services offered on your local node, depending on the options used.

A network manager organizes terminal server nodes into groups based on the number of terminal server nodes in the LAT network. Groups subdivide the LAT network, limiting the number of terminal server nodes that can connect with a given service node.

As many as 256 groups, numbered 0 to 255, can be in the LAT network. By default, all terminal server nodes and nodes supporting outgoing connections belong to group 0. If you enter one group code, you can omit the parentheses. Use the SHOW NODE command for a list of the groups enabled for your service node.

The /GROUPS qualifier has several options. For each option described, you can specify more than one group by:

The available options are:
ENABLE= group-code[,...] Gives the listed groups access to your service node.
DISABLE= group-code[,...] Prevents the listed groups from accessing your service node. The listed groups had been enabled previously for access to your node.
ENABLE= group-code[,...],
DISABLE= group-code[,...] 		This option lets you enable certain groups and disable other groups in one command line: gives access to the groups listed with the ENABLE option and removes access from the groups listed with the DISABLE option. Enclose both ENABLE and DISABLE in parentheses; for example, /GROUP=(ENABLE=(10,12),
DISABLE=(1-30)).

Example 2 shows how to specify the /GROUPS qualifier with the SET NODE command.

/IDENTIFICATION[="identification-string"]

Describes and identifies a node. Service nodes include the identification string in service announcements. A service node announces its services at regular intervals established with the SET NODE command. Entering the LATCP command SHOW NODE or the DECserver command SHOW NODE generates a display that includes this identification string. By default, the identification string is the translation of SYS$ANNOUNCE.

You cannot specify more than 64 ASCII characters in an identification string (a SYS$ANNOUNCE longer than that will be truncated to the first 64 characters). Enclose the string in quotation marks (" ").

/KEEPALIVE_TIMER[=secs]

Controls the maximum interval, in seconds, between idle run messages sent by your local node to another service node to which it has a LAT connection. Your node sends these messages when no other traffic is being generated over the virtual circuit. If the service node acknowledges these messages, your node will continue to monitor the status of the circuit. If your node does not receive acknowledgment, it responds as if the circuit is down.

Use this qualifier only if your node allows outgoing connections (/CONNECTIONS=OUTGOING_ONLY or /CONNECTIONS=BOTH).

The default value is 20. Compaq recommends this value for normal LAN environments. For a heavily loaded LAN, consider using a higher value. Set the timer in the range of 10 to 255. For applications that require quick notification and possible failover of a service node failure, use a lower value. You cannot change this value if active or pending connections exist.

/LARGE_BUFFER

/NOLARGE_BUFFER

Controls whether the LAT software uses large buffers while managing communications between OpenVMS systems (the default).

If you must use the /NOLARGE_BUFFER qualifier (for example, to limit packet sizes to be no larger than the Ethernet maximum), Compaq recommends that you specify this command after all logical LAT links have been created and before the LAT node has been turned on. For example, note the following commands in LAT$SYSTARTUP.COM: 


 $! 
 $! Create each logical LAT link with a unique name and 
 $! unique LAN address (forced with /NODECNET). 
 $! 
 $ LCP CREATE LINK FDDI_1 /DEVICE=FCA0 /NODECNET 
 $ LCP CREATE LINK FDDI_2 /DEVICE=FCB0 /NODECNET 
 $! 
 $! Don't use large buffer support (force packet 
 $! sizes to be no larger than what Ethernet can 
 $! support). 
 $! 
 $ LCP SET NODE /NOLARGE_BUFFER 
 $! 
 $! Turn on the LAT protocol. 
 $! 
 $ LCP SET NODE /STATE=ON

/LOG

/NOLOG (default)

Specifies whether LATCP displays a message confirming that the node's characteristics were modified. If you do not specify the /LOG or /NOLOG qualifier, the default is that no message will be displayed.

/MULTICAST_TIMER[=secs]

Specifies the time, in seconds, between multicast messages sent by a service node. A multicast message announces the services offered by a service node. The minimum value is 10 seconds; the maximum is 180 seconds. The default value is 60.

/NODE_LIMIT=value

/NONODE_LIMIT

Specifies the maximum number of service nodes that your local node can store in its service and node database. Use this qualifier only if your node allows outgoing connections (/CONNECTIONS=OUTGOING_ONLY or /CONNECTIONS=BOTH).

When the database reaches the node limit, no more nodes are added to the database when your local node receives service announcement messages. You can ensure that the node limit is not reached by using the /USER_GROUPS qualifier to restrict access from the local node to other service nodes on the network.

If you do not specify either the /NODE_LIMIT=value or /NONODE_LIMIT qualifier, the default is no limit. A value of 0 indicates no limit.

/QUEUE_LIMIT=value

Sets a limit on the number of entries (incoming LAT connections only, not outgoing printer connections) that are queued on the system. The queue limit value can range from 0 to 200, with a default of 24. A value of 0 indicates that no queuing is allowed.

/RETRANSMIT_LIMIT[=count]

Specifies the number of times your local node repeats transmission of a message to a service node after a transmission fails. If the transmission is still unsuccessful after these attempts, the virtual circuit between your local node and the service node terminates, along with all sessions associated with the virtual circuit.

Use this qualifier only if your node allows outgoing connections (/CONNECTIONS=OUTGOING_ONLY or /CONNECTIONS=BOTH).

Specify a value in the range of 4 to 120. The default is 8. The value you choose depends on the type of physical link used for your network, as well as the amount of traffic on the network. See your network manager for a suggested value. You cannot change this value if active or pending connections exist.

/SERVICE_RESPONDER

/NOSERVICE_RESPONDER

Specifies whether your system responds to special LAT multicast messages that request service information. Some terminal servers do not have their own service and node database. When a user on such a terminal server requests a connection to a service, the server sends a LAT multicast message requesting names of nodes that offer the requested service. Service responder nodes reply with the requested information.

If you specify /SERVICE_RESPONDER, your system responds to the special LAT multicast messages. (If you specify /NOSERVICE_RESPONDER, your system does not respond to those messages.) Compaq recommends that you set up only one or two nodes in the LAN as service responder nodes. The nodes should have the largest databases in the LAN. Use this option only if your node allows outgoing connections (/CONNECTIONS=OUTGOING_ONLY or /CONNECTIONS=BOTH).

If you do not specify either the /SERVICE_RESPONDER or /NOSERVICE_RESPONDER qualifier, the default is that your system will not respond to the special LAT multicast messages.

/SESSION_LIMIT=option

Specifies the maximum number of simultaneous sessions across all local-access ports. This limit does not affect the use of dedicated and application ports. It affects interactive port creation only, limiting the amount of resources consumed by interactive users creating new sessions.

The options for the /SESSION_LIMIT qualifier are:
INCOMING= value Sets the session limit for incoming connections only. The default is no limit (a value of 0).
OUTGOING= value Sets the session limit for outgoing connections only. The default is no limit (a value of 0).
INCOMING= value,OUTGOING= value Sets the limit for both outgoing and incoming connections. Enclose both options in parentheses; for example, /SESSION_LIMIT=(INCOMING=20, OUTGOING=25).

If the limit is reached, interactive users cannot create new sessions. In this case, increase the session limit or disconnect any connections that are no longer being used.

Specify a value in the range of 0 to 255. Specifying 0 leaves no limit on the number of sessions that can be created. To prevent sessions from being created, use the /CONNECTIONS qualifier.

Not specify the /SESSION_LIMIT qualifier causes no limit on the number of incoming and outgoing sessions. This is the default.

/STATE=option

Specifies whether LAT connections are allowed. The three options for STATE are:
ON Starts the LAT port driver (and LAT protocol software) on your node.

Compaq strongly recommends that the LATCP command SET NODE/STATE=ON be executed before any LTA application or dedicated ports are created (use the format provided in SYS$MANAGER:LAT$SYSTARTUP.TEMPLATE) for two reasons:

  • It ensures that LTDRIVER will delete any leftover LTA devices that have a reference count of 0 and are explicitly marked for deletion (using the $DASSGN system service or the LATCP command DELETE PORT, for example). Because every LATCP management port (LATCP$MGMT_PORT) that was created by the previous LATCP invocation is deleted, no conflicts result with the LAT application ports or newly created dedicated ports.
  • The deletion of leftover LTA devices with a reference count of 0 minimizes the use of nonpaged pool memory.
OFF Stops the LAT port driver (and LAT protocol software) on your node. Any existing LAT connections are aborted. Any characteristics that you changed or set with LATCP are lost.

To start the LAT protocol on your node again, invoke LAT$STARTUP.COM. (Refer to the OpenVMS System Manager's Manual for more information.) The LAT characteristics defined in LAT$SYSTARTUP.COM will take effect.

SHUT Specifies that new LAT connections cannot be created on your local node, but existing connections may continue. The LAT protocol continues running only until the last active session disconnects, (after which LTDRIVER will stop). At that time, your node changes to the OFF state.

Caution
If you stop the LAT software by specifying either the SET NODE/STATE=OFF or SET NODE/STATE=SHUT command, the LAT print symbiont (LATSYM) will shut down all print queues that it is processing. The system will then generate an OPCOM message indicating that the print queues are stopped. You must manually restart those print queues.

If you do not specify the /STATE=option qualifier, the default is that the LAT port driver and LAT protocol software on your node will be started (ON).

/UNIT_NUMBER_MAXIMUM=value

Specifies the maximum unit number for a LAT device. For example, if you specify 140, then LTA140: will be the device with the highest unit number. Specify a value that is high enough to accommodate all devices that may be in use simultaneously. When the number of devices in use exceeds the value you specify, the system gives certain LAT devices unit numbers that exceed your maximum.

Also note the following points:

The range of maximum unit numbers is 99 to 9999. The default is 9999. Note that each time you specify the /UNIT_NUMBER_MAXIMUM qualifier, the LTA device seed value is reset to approximately half of the newly specified maximum unit number.

/USER_GROUPS=option[,...]

Restricts access (from the local node) to service nodes in the network that belong to the specified groups. Your local node can access only those service nodes associated with the user groups specified. The /USER_GROUPS qualifier also serves to limit the number of nodes stored in your node's node database. (The local node only stores information about the nodes and services that belong to at least one of the specified user groups.) By default, all LAT service nodes belong to group 0.

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