![[Digital logo]](../../IMAGES/DIGITAL-LOGO.GIF){kind=logo}
![[HR]](../../IMAGES/REDBAR.GIF)
Transfers control from your current process to the specified process. The LATCP command ATTACH is similar to the DCL command ATTACH. For example, from the DCL command level you can enter the DCL command SPAWN to create a LATCP subprocess without ending your DCL session, execute several LATCP commands at the LATCP prompt, then use the ATTACH command to return to DCL.
ATTACH [process-name]
process-name
Specifies the name of a parent process or spawned subprocess to which control passes. The process must already exist, be part of your current job, and share the same input stream as your current process.Process names can contain from 1 to 15 alphanumeric characters. If a connection to the specified process cannot be made, LATCP displays an error message.
If you specify the /PID qualifier, do not use the process name parameter. If you omit the /PID qualifier, you must use the process name parameter.
To display processes, use the DCL command SHOW SYSTEM.
/PID=pid
Specifies the process identifier (PID) of the process that will have terminal control. When you specify a PID, you can omit the leading zeros. If you specify a PID, do not use the process name parameter. If you omit the / PID qualifier, you must use the process-name parameter.
The ATTACH command allows you to connect your input stream to another process. You can use ATTACH to change control from one process to another. For example, you can use ATTACH to change control from LATCP to the DCL command level (see the following example). While you are at the DCL command level, LATCP remains in a hibernation state until you use ATTACH to return to it.You cannot use this command if you are logged in to a captive account. (A captive account is an account set up to restrict user access to the system. You cannot access the DCL command level from a captive account.) You cannot specify both a process name and the /PID qualifier.
$ SET PROCESS/NAME="TOP_LEVEL" $ SPAWN RUN SYS$SYSTEM:LATCP LATCP> SHOW NODE/ALL . . . LATCP> ATTACH "TOP_LEVEL" $
In this example, the user enters the DCL command SPAWN to create a LATCP subprocess and uses LATCP to display the status of all nodes known to the local node. After using LATCP, the user enters the ATTACH command to return to the DCL command level.
Creates the LAT data links, which are connections to LAN devices, such as Ethernet or FDDI (Fiber Distributed Data Interface) controllers, that you want your node to use. You must have OPER privilege to use this command.
CREATE LINK link-name
link-name
Specifies a name for a LAT data link. A link name can have up to 16 ASCII characters. The characters allowed are as follows:
- Alphanumeric characters: A--Z, a--z, 0--9
- A subset of the international character set: ASCII codes 192--253
- Punctuation characters: dollar sign ($), hyphen (-), period (.), and underscore (_)
You can create a maximum of eight links on your local node. Use the SHOW LINK command for a list of the link names that are defined for your node.
/DECNET (default)
/NODECNET
Directs LAT protocol to use the DECnet data link address (/DECNET) or the hardware address (/NODECNET) when starting the LAN controller. If you do not specify the /DECNET or /NODECNET qualifier, the default is that the LAT protocol will use the DECnet data link address.Note that if you enter the CREATE LINK command with the /DECNET qualifier and receive an error message indicating a "bad parameter value," it means the SCSSYSTEMID system parameter is set to an illegal value. To change the value of this parameter, use the following formula:
(1024 * a) + nIn the formula, a is the DECnet area and n is the DECnet computer number. If the value is outside the range of 1025 to 65535, the LAT protocol cannot start.
When you use the /NODECNET qualifier, the LAN device driver code determines which address to use. For example:
- If SCSSYSTEMID is set to 0 but DECnet is already running on an Ethernet controller, the LAN device code allows LAT to use the same address as DECnet (AA-00-04-00-xx-xx).
- If SCSSYSTEMID is set to 0 and DECnet is not running, the 08-00-2B-xx-xx-xx address is used (a different address format is used if your LAN controller is supplied by a vendor other than Digital).
- If the setting for SCSSYSTEMID is the same as the DECnet node number and DECnet is not running, the LAN device code forces LAT to use the AA-00-04-00-xx-xx address.
If DECnet is configured on the system (or if the system is part of a cluster), SCSSYSTEMID may contain a nonzero value. This is a problem only when the system has 2 or more LAN controllers connected to the same logical LAN.
For example, if your system has an FDDI controller and an Ethernet controller, your site may be configured so that the FDDI ring attached to the FDDI controller and the Ethernet segment attached to the Ethernet controller are bridged by a 10/100 LAN bridge (FDDI-to-Ethernet). In this configuration, it is impossible to run LAT over both controllers.
In such a configuration, you must run LAT and DECnet over the same controller if SCSSYSTEMID is not 0. If you fail to do so, DECnet starts first, which in turn causes the LAT startup on the other controller to fail. This failure occurs because LAT startup tries to use the AA-00-04-00-xx-xx address (the DECnet LAN address) but is prevented from doing so by the data link layer. The LAT startup fails because DECnet is already using this address on a different controller. (In a single logical LAN, all data link addresses must be unique. In this setup, both controllers try to use the same address, which is then not unique.)
The following command (which creates the LAT link) also fails because the LAN driver tries to use the address based on SCSSYSTEMID:
LATCP> CREATE LINK LAT$LINK_2 /NODECNETIf SCSSYSTEMID is set to 0, configuring LAT and DECnet on different controllers is possible. However, in a cluster environment, SCSSYSTEMID cannot be set to 0.
/DEVICE=device-name
Specifies the LAN controller device name for a LAT data link (for example, XEB0:). Only one LAT data link can be associated with a LAN controller. If you enter the CREATE LINK command without the /DEVICE qualifier, LATCP attempts to find an available controller by using a list of possible LAT data link device names. Digital advises that you specify a default device name by defining the LAT$DEVICE logical name./LOG
/NOLOG (default)
Specifies whether LATCP displays a message confirming that the link was created. If you do not specify the /LOG or /NOLOG qualifier, the default is that no message will be displayed./STATE=option
Specifies whether the link will be available for use. STATE can have two options:
ON Specifies that the created link will be available for use with the LAT protocol running. OFF Specifies that the created link will not be available for use. If you do not specify the /STATE=option qualifier, the default is that the created link will be available for use (ON).
The CREATE LINK command creates a link, or connection, for an OpenVMS node and a local area network (LAN) device (for example, an Ethernet or FDDI controller) and assigns a name to that link. An OpenVMS node can have eight LAN links. Each link must operate on a separate LAN controller and have its own LAN hardware.If you do not explicitly create a link with this command before entering the SET NODE/STATE=ON command, LATCP automatically creates a link for you. LATCP names the link LAT$LINK and assigns it to the first available LAN controller or LAT$DEVICE, if defined. To establish additional links, use the CREATE LINK command.
Whenever you create a link, specify the LAN controller device name.
Use the SET LINK command to modify link characteristics.
LATCP> CREATE LINK NETWORK_A /DEVICE=XEB0: /STATE=ON
This command creates an Ethernet link named NETWORK_A. It specifies the Ethernet controller device XEB0 for that link. The link will be available for use.
Creates a logical port on your local node that connects with a remote device on a terminal server. Alternatively, this command creates a logical port on your local node that connects with a specific service. The service can be offered by a terminal server or associated with one or more dedicated ports on a remote LAT service node.You must have OPER privilege to use this command.
CREATE PORT [port-name]
port-name
Specifies the port name in the form LTAn:, where n is a unique number from 1 to 9999. If the port you specify already exists, LATCP returns the following error message:%LAT-W-CMDERROR, error reported by command executor -SYSTEM-F-DUPLNAM, duplicate nameIf you do not specify the port name, you must specify the /LOGICAL qualifier.
Notes
When creating a port, note the following:
- Digital recommends that you assign a logical name when creating a port, instead of specifying a specific LTA device.
- You cannot use the CREATE PORT and SET PORT commands, along with the DCL command SET TERMINAL, to change the characteristics of a DECserver port unless there is an existing LAT connection to that DECserver.
/APPLICATION
Specifies that a logical port on your node is an application port. It can be used to connect to a remote device (typically a printer) on a terminal server or to a dedicated port on another LAT service node.If you do not specify a port type, the default port type is APPLICATION.
Note
By default, LATCP creates application LAT devices with the HANGUP terminal characteristic. However, if you want to apply the NOHANGUP characteristic to application LAT devices, you can do so by entering specific LATCP and DCL commands. For example:$ LCP :== $LATCP $ LCP CREATE PORT LTA1234 $ LCP SET PORT LTA1234 /APPLICATION /NODE=terminal-server /PORT=server-port $ SET TERMINAL LTA1234 /PERMANENT /NOHANGUPNote that you can insert the SET TERMINAL command in the SYS$MANAGER:LAT$SYSTARTUP.COM file (enter the command for each LAT device that requires the NOHANGUP characteristic).
/DEDICATED
Specifies that a logical port on your local node is dedicated to an application service. When users on a terminal server (or on another node that supports outgoing connections) request a connection to this service name, they are connected to the dedicated port. See the OpenVMS I/O User's Reference Manual for a description of programming an application service.After creating a dedicated port on a node, use the SET PORT /SERVICE command to map this port to a service.
/LIMITED
Specifies that a logical port on your local node is limited to a service in the same way a port created using the /DEDICATED qualifier is dedicated to an application service. The difference is that ports created using the /LIMITED qualifier are under the control of the system login image (LOGINOUT.EXE) instead of an application program (a user who connects to a limited service and is assigned to a limited port receives the Username: prompt).Using the /LIMITED qualifier, you can create a limited number of ports and map them to a specific service offered by the host system. If users are logged in to all of the limited ports for the service, no more connections are allowed to that service (terminal server users receive a "service in use" message).
/LOG
/NOLOG (default)
Specifies whether LATCP displays a message confirming that the port was created. If you do not specify the /LOG or /NOLOG qualifier, the default is that no message will be displayed./LOGICAL=(NAME=logical-name[,TABLE=table][,MODE=mode])
Specifies a logical name to be associated with the actual name of the created port. You must specify a logical name if you do not specify a port name.
Note
If you have sufficient privileges to create a port, but lack the privilege to assign a logical name, the port will still be created.
You can specify one of the following options for the TABLE keyword:
GROUP Places the logical name in the group logical name table. You must have GRPNAM or SYSPRV privilege to place the logical name in the group logical name table. JOB Places the logical name in the jobwide logical name table. PROCESS Places the logical name in the process logical name table. This is the default. SYSTEM Places the logical name in the system logical name table. You must have SYSNAM or SYSPRV privilege to place a name in the system logical name table. You can also specify the name of a specific table. For example, you could specify LNM$PROCESS, which would be the equivalent of specifying PROCESS.
Options for the MODE keyword are:
EXECUTIVE Creates an executive mode logical name. You must have SYSNAM privilege to create an executive mode logical name. SUPERVISOR Creates a supervisor mode logical name. USER Creates a user mode logical name. The access mode associated with the logical name is determined by maximizing the access mode of the caller with the access mode specified by the MODE keyword: the mode with the lower privilege is used.
You cannot specify an access mode with a privilege higher than that of the table containing the logical name. However, if your process has SYSNAM privilege, then the specified access mode is associated with the logical name regardless of the access mode of the caller.
If you omit the MODE keyword, the access mode of the caller is associated with the logical name.
The CREATE PORT command creates a logical LAT port for your local node. You can set up the port as an application port that is later mapped to a remote printer (or other device) on a server, or you can set up the port to be mapped to a dedicated port on a remote LAT service node. See Example 1.Alternatively, you can set up the port as a dedicated port for a special service on a LAT service node. See Example 2.
You can also create the port as a limited port, using the /LIMITED qualifier.
After creating a port, use the SET PORT command to associate (map) the port with a queue or a service. (See the discussion that follows Example 1.) Ordinarily, you create and set ports in the LAT site-specific startup procedure, LAT$SYSTARTUP.COM. See the OpenVMS System Manager's Manual for more details.
Note
When using the CREATE PORT command to create an application port (for example, CREATE PORT LTA5001: /APPLICATION), you might receive an error message similar to the following:%LAT-W-CMDERROR, error reported by command executor -SYSTEM-F-DUPLNAM, duplicate nameThis error occurs because the LAT application port that you are trying to create has already been created by some other application. That other application could be LATCP itself because LATCP's port, LATCP$MGMT_PORT, is used to communicate with LTDRIVER.
You can avoid creating duplicate ports in two ways:
- Use the SET NODE/DEVICE_SEED command to move the lower boundary of the device unit number range beyond the LTA devices that you are intending to use as application ports. (By default, LTA device units that originate from the $ASSIGN system service to LTA0: have unit numbers that fall within a range from 1 through 9999.) For example, if you know that all LTA devices from LTA7000: onward are not used as application ports, you could enter the following commands:
LATCP> SET NODE/DEVICE_SEED=7000 LATCP> CREATE PORT LTA5001:/APPLICATION . . . LATCP> CREATE PORT LTA5010:/APPLICATIONFor more information, see the description of the /DEVICE_SEED qualifier in the SET NODE reference section.- Execute the LATCP command SET NODE/STATE=ON (either interactively or in a program) before any LTA application or dedicated ports are created. Because every LATCP management port (LATCP$MGMT_PORT) created by the previous LATCP invocation is deleted, no conflict exists with LAT application ports or newly created dedicated ports.
For more information, see the description of the /STATE qualifier in the SET NODE reference section.
Examples
LATCP> CREATE PORT LTA22: /APPLICATION
LATCP> CREATE PORT LTA21: /DEDICATED
LATCP> CREATE PORT /LOG /APPLICATION - _LATCP> /LOGICAL=(NAME=MAIL_PORT, TABLE=PROCESS, MODE=SUPERVISOR)
$ LCP :== $LATCP $ LCP CREATE SERVICE/LIMITED ONLY_ONE $ LCP CREATE PORT/LIMITED LTA1234: $ LCP SET PORT LTA1234: /SERVICE=ONLY_ONE
Creates a service on a service node. You must have OPER privilege to use this command.
CREATE SERVICE [service-name]
service-name
Specifies a LAT service name. By default, a service name is the name of the local node you defined with the SET NODE command.The service name can be from 1 to 16 ASCII characters in length. The characters allowed are as follows:
- Alphanumeric characters: A--Z, a--z, 0--9
- A subset of the international character set: ASCII codes 192--253
- Punctuation characters: dollar sign ($), hyphen (-), period (.), and underscore (_)
/APPLICATION
Specifies that the created service is an application service. An application service offers a specific application on the service node rather than a general interactive service. You can define a dedicated port for the service by using the CREATE PORT and SET PORT commands./IDENTIFICATION[="identification-string"]
Describes and identifies a service. Service nodes include the identification string in service announcements. A service node announces its services at regular intervals established with the SET NODE command. Entering the LATCP SHOW NODE command or the DECserver SHOW NODE command generates a display that includes this identification string. By default, the identification string is a translation of SYS$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 ("").
/LIMITED
Specifies that the service is a limited service, using devices assigned the limited characteristic and associated with (mapped to) this limited service. This qualifier is used in conjunction with the SET PORT /LIMITED command./LOG
/NOLOG (default)
Specifies whether LATCP displays a message confirming that the service was created. If you do not specify the /LOG or /NOLOG qualifier, the default is that no message will be displayed./STATIC_RATING=rating
/NOSTATIC_RATING
Enables or disables dynamic service ratings. A dynamic service rating means that a LAT algorithm calculates the availability of a service dynamically, based on the overall level of activity of the node that offers the service and the amount of memory. When a terminal server or node requests a connection to a service that is offered on two or more service nodes, the requesting node selects the service node with the highest (most favorable) service rating. This selection process is called load balancing.The dynamic service rating, which is the default, is usually adequate for efficient load balancing on the LAT network. However, when necessary, you can use the /STATIC_RATING qualifier to disable dynamic service ratings so that you can specify a static (fixed) rating. That static rating value does not change until the dynamic service rating is reenabled.
Use the static rating to direct users away from or toward your node temporarily. Static ratings range from 0 to 255. Specify a low value to make the local service node less likely to be used; specify a high value to make the local service node more likely to be used.
If you do not specify either the /STATIC_RATING or /NOSTATIC_RATING qualifier, the default is that the LAT software uses the dynamic service rating.
Limited and application services do not rely exclusively on the dynamically calculated service rating. Instead, they use a portion of the dynamic rating based on how many ports are available for the service. For example, if a limited service has 50 percent of its ports available, the dynamic service rating will be scaled, halved, and then added to 105. When ports are available, the rating will always be above the value 105.
When all ports for a limited or application service are in use, the rating will be based on the scaled dynamic rating and the number of free queue slots on the local node. The rating will always be less than 90.
This rating procedure for limited and application services follows the terminal server rating algorithm for services and available ports that the service offers, while at the same time taking into account the availability of the node (which is the factor used to calculate the dynamic rating).
If your system is licensed for a specific number of units (where only a fixed number of users can log in to the system regardless of how the login limit is set), then all dynamic ratings become 0 when all OpenVMS license units have been consumed. (This forces all node service ratings to the lowest possible value when logins are not possible because all OpenVMS license units have been consumed.)
Note as well that the LAT software transmits a service announcement message when a user logs in to or out of the system. This allows the system to more quickly provide information about service rating changes that result from a login or logout operation.
The CREATE SERVICE command creates a service that a service node offers to terminal servers (and nodes that support outgoing connections) on the LAT network. The service can be a general timesharing service that offers all the resources of the service node, or it can be an application service that offers a specific application on the service node. The number of services that you can create with the CREATE SERVICE command depends on the availability and capability of specific resources.The following table lists the maximum number of services your node can offer and still be recognized by the DECserver terminal server, depending on the model number.
DECserver Terminal Server Maximum Number of Services
Offered by NodeModel 100 8 Model 200 64 Model 300 64 Model 90TL 64 Model 700 64 Model 500 127
Note
If you create more than the maximum number of services supported by a specific DECserver model, that server will not recognize your node.
To create an application service, use the /APPLICATION qualifier. In addition, define a dedicated port by using the CREATE PORT and SET PORT commands. Most often, a system manager creates services in LAT$SYSTARTUP.COM, the site-specific LAT configuration procedure. (See the OpenVMS System Manager's Manual for further information on creating an application service. The OpenVMS I/O User's Reference Manual shows how to program an application service.)
Several service nodes can share one service name. A shared service name is especially useful in a cluster environment because it allows the cluster to be known by a single cluster name. When a user logs in, the terminal server connects to the least busy node offering that service.
You can modify the service characteristics with the SET SERVICE command.
Examples
LATCP> CREATE SERVICE/STATIC_RATING=195 SALES
LATCP> CREATE SERVICE/APPLICATION GRAPHICS
$ LCP :== $LATCP $ LCP CREATE SERVICE/LIMITED ONLY_ONE $ LCP CREATE PORT/LIMITED LTA1234: $ LCP SET PORT LTA1234: /SERVICE=ONLY_ONE
6048P027.HTM OSSG Documentation 26-NOV-1996 12:42:58.82
Copyright © Digital Equipment Corporation 1996. All Rights Reserved.