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An agent program can use the ACMS$CANCEL_CALL service to cancel tasks. The ACMS$CANCEL_CALL service can be used only to cancel tasks that are started with the ACMS$START_CALL service. ACMS$START_CALL returns a call ID that can be used with the ACMS$CANCEL_CALL service to stop a task prematurely.
For example, use ACMS$CANCEL_CALL to cancel tasks when a terminal user presses [Ctrl/Y]. ACMS expects a task to be canceled when the terminal user presses [Ctrl/Y] (or [Ctrl/C], if the server is not running a task that enables a [Ctrl/C] handler). If an agent program does not use ACMS$CANCEL_CALL to cancel any active tasks when a user presses [Ctrl/Y], then [Ctrl/Y] cancels are ignored and the tasks will run to completion.
You can use the ACMS$CANCEL_CALL service to send multiple cancel requests to a single task instance. For example, consider the case where an agent program starts a menu task for a user. During the day, the user selects tasks from the menu task to perform the user's business transactions. Because the user might need to press [Ctrl/C] to cancel more than one task called by the menu task, ACMS allows the agent program to call the ACMS$CANCEL_CALL service many times. See Compaq ACMS for OpenVMS Writing Applications for more information on how ACMS processes task cancellation requests for tasks called by other tasks.
5.4 ACMS$CALL
Submits an ACMS task. This service completes when the task ends. If you
use the asynchronous ACMS$CALL_A service, it is also necessary to call
the ACMS$WAIT service. See Chapter 2 for an explanation of the
ACMS$WAIT service.
If application reprocessing is required, the agent program must use the ACMS$GET_PROCEDURE_INFO service before calling ACMS$CALL.
ACMS$CALL ([submitter_id.rq.r],
procedure_id.rq.r,
[arguments.rz.r],
[tid.ro.r])ACMS$CALL_A ([submitter_id.rq.r],
procedure _id.rq.r,
[arguments.rz.r],
[tid.ro.r],
[comp_status.wq.r],
[efn.rbu.r],
[astadr.szem.r],
[astprm.rz.v])
submitter_id
The submitter ID corresponding to a signed-in submitter. The submitter ID is returned on the ACMS$SIGN_IN service.This parameter is optional for agent programs that do not use ACMS$SIGN_IN. Use of the default submitter feature, however, is not recommended for new development. See Section 2.1.6 and Section 2.1.7 for a discussion of this point.
procedure_id
The procedure ID of the task to call. You obtain this procedure ID by calling the ACMS$GET_PROCEDURE_INFO service.arguments
The list of arguments to pass, if any. (See Section 5.1 for more information about using the argument list.)This is a standard OpenVMS argument list that contains:
- selection_string.rt.dx
An agent program passes data to the ACMS$SELECTION_STRING system workspace in a task using the selection string argument. Initialize the selection string argument in the argument list with the address of an OpenVMS string descriptor that references the selection string data.
The selection string argument is optional. If the agent program does not pass any information to the ACMS$SELECTION_STRING workspace, the agent program must set this argument to zero. When an agent program does not supply a selection string argument, ACMS initializes the ACMS$SELECTION_STRING workspaces with spaces.- extended_status.wt.dx
When ACMS ends a task, it returns the message text associated with the task's final completion status back to the agent program. To access the message text after a task has completed, initialize the extended status argument with the address of an OpenVMS string descriptor into which ACMS can store the data.
The extended status argument is optional. If the agent program does not need to access the task's completion status message text, set this argument to zero. If you do not supply the address of a string descriptor in this argument, ACMS does not return the message text from the application to the agent program.
Note
The extended status string cannot be filled if the application execution controller (EXC) cannot start a task (for example, if the EXC terminates abnormally, if a DECnet link terminates, or if EXC runs out of virtual memory). The extended status string also cannot be filled if the submitter services detect an error --- for example, if the submitter services receive an invalid procedure argument list, there is an internal error, or a task ends because the EXC terminated abnormally before completing the task.- I/O argument
There are several ways to pass I/O information to a task. The preferred method is to pass the exchange I/O ID as the I/O argument. ACMS supports the use of the other methods for compatibility with previously-developed agent programs.
The methods of passing I/O information to the task are:
- exchange_io_id.rq.r
The I/O argument can be an exchange I/O ID returned from the ACMS$INIT_EXCHANGE_IO service.- terminal_name.rt.dx
The I/O argument can also be a terminal specification for tasks that perform request I/O or terminal I/O.- stream_id.rq.r
For stream I/O tasks, you can initialize this argument with the address of the stream ID.- For tasks that do not perform I/O, you can set this argument to zero. If the agent program does not pass any workspaces to the task, it can omit this argument.
- workspaces
You supply workspaces to tasks in the fourth and successive arguments of the task's argument list. The workspace supplied in the fourth argument is used to initialize the first task argument workspace defined in the TASK ARGUMENTS clause in the task definition. The fifth argument is used to initialize the second workspace defined as a task argument in the TASK ARGUMENTS clause, and so on. Workspaces are passed to the task by descriptor. Therefore, initialize each workspace argument with the address of an OpenVMS string descriptor that references the workspace data. The read, write, or modify access to each workspace is determined by the TASK ARGUMENTS clause in the task:
- workspace_n.rt.dx
- workspace_n.wt.dx
- workspace_n.mt.dx
Workspace arguments are optional. If you do not want to supply one or more workspaces to a task, initialize the corresponding arguments in the task's argument list to zero. If you do not supply data to a workspace defined in a task as a TASK ARGUMENT, ACMS initializes that workspace with the default contents from the .TDB or with zeros.
See Section 5.1 and Section 5.2 for detailed information on how to pass a workspace to a task. See the VR_AGENT.C program and the VR_FAST_CHECKIN_TASK.TDF task definition in the ACMS$EXAMPLES directory for an example of an agent program calling a task.tid
The transaction ID (TID) that the $START_TRANS service returns.
The parameters comp_status.wq.r, efn.rbu.r, astadr.szem.r, and astprm.rz.v are asynchronous service arguments. See Chapter 2 for a discussion of these parameters.
If an agent program attempts to supply more workspace arguments to a task than there are TASK ARGUMENT workspaces defined for that task, then the ACMS$CALL and ACMS$START_CALL services complete and return the "%ACMS-F-ERRREADARG, Error during task initialization: cannot read an argument in argument list" error. The agent program can use the ACMS$GET_PROCEDURE _INFO service to determine the correct number of TASK ARGUMENT workspaces defined for the task.
The return status codes indicating success or failure of the call follow:
Status Severity Level Description ACMS$_NORMAL Success Normal successful completion. ACMS$_PENDING Informational Successful operation pending asynchronous completion. The final status is in the completion status block. ACMS$_CALL_CANCELLED Error Task was cancelled by task submitter. ACMS$_ERRREADARG Error Error during task initialization; cannot read an argument in the argument list. ACMS$_EXCPTN_STEPACTN Error Exception results from a step action in the task definition. ACMS$_NEED_DEVICE Error Task requires a device; none provided. ACMS$_NEED_DEVORRR Error Task requires a device name or RR server. ACMS$_NEED_IOID Error Task is defined with I/O. ACMS$_INSUFPRM Error Not enough arguments were passed to this service. ACMS$_INTERNAL Error Internal error. ACMS$_INVARGLST Error The argument list is invalid. ACMS$_INVASTADR Error The AST address was invalid. ACMS$_INVCMPSTS Error The completion status block was invalid. ACMS$_INVEFN Error The event flag was invalid. ACMS$_INVPROCID Error The procedure ID was invalid. ACMS$_INVSUB Error The submitter ID was invalid. ACMS$_INVTID Error Returned if ACMS does not have access to the Transaction ID (TID). The symbol is not defined as a universal symbol and will result in a link error if declared and accessed as a global symbol. This symbol has not been defined since ACMS Version 3.3b. ACMS$_NOSUCH_PROC Error There is no such procedure in the package. ACMS$_NOSUCH_PKG Error There is no such application defined. ACMS$_NOTAVAIL Error The feature is not yet available. ACMS$_NOTRANSADB Error No transaction support in the application database file (.ADB). ACMS$_NOTRANSNODE Error ACMS does not support transactions on the application node. ACMS$_NTSNIN Error Submitter was not signed in. ACMS$_OPR_CANCELLED Error Task canceled by system operator. ACMS$_SRVDEAD Error The server or EXC stopped unexpectedly. ACMS$_SRVNOTFOUND Error The server was not found. ACMS$_SIGNOUT_ACTIVE Error A sign-out is active. ACMS$_SYNASTLVL Error Synchronous services may not be called from AST level. ACMS$_TASKNOTCOMP Error Task is not composable. ACMS$_TRANSTIMEDOUT Error Transaction did not complete within specified time limit. ACMS$_USERMODE Error This service must be called from user mode.
5.5 ACMS$CANCEL_CALL
Cancels a task that was started by the task submitting agent program.
This service only cancels tasks that were started with ACMS$START_CALL.
The agent program must also use the ACMS$WAIT_FOR_CALL_END service with
this service to get notification of the call canceling.
Use ACMS$CANCEL_CALL to cancel tasks when a terminal user presses [Ctrl/Y]. ACMS expects a task to be canceled when the terminal user presses [Ctrl/Y] (or [Ctrl/C], if the server is not running a task that enables a [Ctrl/C] handler). If an agent program does not cancel any active tasks when [Ctrl/Y] is pressed, then [Ctrl/Y] cancels are disabled and the tasks run to completion.
The effect of this call might not be immediate or successful, due to the asynchronous nature of ACMS. |
ACMS$CANCEL_CALL ([submitter_id.rq.r],
call_id.rq.r,
[reason_code.rlu.r])ACMS$CANCEL_CALL_A ([submitter_id.rq.r],
call _id.rq.r,
[reason_code.rlu.r],
[comp_status.wq.r],
[efn.rbu.r],
[astadr.szem.r],
[astprm.rz.v])
submitter_id
The identification of the task submitter calling the task. The ACMS$SIGN_IN service returns this ID. This parameter is optional for agent programs that do not use ACMS$SIGN_IN. Use of the default submitter feature, however, is not recommended for new development. See Section 2.1.6 and Section 2.1.7 for discussions of this point.call_id
The identification returned by ACMS$START_CALL. The call must be started by the same submitter as the one using the ACMS$CANCEL_CALL service.reason_code
The reason code contains the reason for the cancel request. The parameter is passed to the application execution controller. The default is the following:
ACMS$_CALL_CANCELLED: the task was canceled by the task submitter.The reason code is the extended status of the call and the completion status returned on the ACMS$WAIT_FOR_CALL_END service.
The parameters comp_status.wq.r, efn.rbu.r, astadr.szem.r, and astprm.rz.v are asynchronous service arguments. See Chapter 2 for a discussion of these parameters.
The return status codes indicating success or failure of the call follow:
Status Severity Level Description ACMS$_NORMAL Success Normal successful completion. ACMS$_PENDING Informational Successful operation pending asynchronous completion. The final status is in the completion status block. ACMS$_INSUFPRM Error Not enough arguments were passed to this service. ACMS$_INTERNAL Error Internal error. ACMS$_INVASTADR Error The AST address was invalid. ACMS$_INVCALLID Error The call ID was invalid. ACMS$_INVCMPSTS Error The completion status block was invalid. ACMS$_INVEFN Error The event flag was invalid. ACMS$_INVREACOD Error The reason code parameter was invalid. ACMS$_INVSUB Error The submitter ID was invalid. ACMS$_NTSNIN Error Submitter was not signed in. ACMS$_OBSCALLID Error The call ID is obsolete. ACMS$_SIGNOUT_ACTIVE Error A sign-out is active. ACMS$_SYNASTLVL Error Synchronous services may not be called from AST level. ACMS$_USERMODE Error This service must be called from user mode.
5.6 ACMS$GET_PROCEDURE_INFO
Finds and returns the procedure ID for the task, the number of
workspace arguments the agent program can pass to a task in an ACMS
application, and the I/O method (forms, terminal, request, stream, or
none).
If application reprocessing is necessary, use ACMS$GET_PROCEDURE_INFO before using ACMS$CALL, ACMS$CALL_A, ACMS$START_CALL, or ACMS$START_CALL_A.
ACMS$GET_PROCEDURE_INFO ([submitter_id.rq.r],
procedure.rt.dx,
package.rt.dx,
item_list.rx.r)ACMS$GET_PROCEDURE_INFO_A ([submitter_id.rq.r],
procedure.rt.dx,
package.rt.dx,
item _list.rx.r,
[comp_status.wq.r],
[efn.rbu.r],
[astadr.szem.r],
[astprm.rz.v])
submitter_id
The identification of the task submitter that the ACMS$SIGN_IN service returns.This parameter is optional for agent programs that do not use ACMS$SIGN_IN. Use of the default submitter feature, however, is not recommended for new development. See Section 2.1.6 and Section 2.1.7 for discussions of this point.
procedure
The name of the task for which you want to find information. The name passed must be in capital letters, but can include trailing blanks.package
The name of the application from which you want to select the task. The name passed must be in capital letters, but can include trailing blanks. However, if the package parameter is a logical name, then the equivalence name or names cannot contain trailing blanks.item_list
The list of one or more item descriptors that describe the task I/O method, WAIT/DELAY information, or procedure ID. An item descriptor has the following format:
Item descriptors have the following characteristics:
The possible item codes are:
You must end the list with an item descriptor that has an item code of zero.
The parameters comp_status.wq.r, efn.rbu.r, astadr.szem.r, and astprm.rz.v are asynchronous service arguments. See Chapter 2 for a discussion of these parameters.
The return status codes indicating success or failure of the call follow:
Status Severity Level Description ACMS$_NORMAL Success Normal successful completion. ACMS$_PENDING Informational Successful operation pending asynchronous completion. The final status is in the completion status block. ACMS$_INSUFPRM Error Not enough arguments were passed to this service. ACMS$_INTERNAL Error Internal error. ACMS$_INVASTADR Error The AST address was invalid. ACMS$_INVBUFADR Error The buffer address in an item descriptor was invalid. ACMS$_INVCMPSTS Error The completion status block was invalid. ACMS$_INVEFN Error The event flag was invalid. ACMS$_INVITEMCODE Error The item code in an item descriptor was invalid. ACMS$_INVITEMDESC Error An item descriptor in the item list was invalid. ACMS$_INVITEMLIST Error The item list was invalid. ACMS$_INVPACKAGE Error The application name was invalid. ACMS$_INVPROCEDURE Error The procedure name was invalid. ACMS$_INVRETLEN Error The return length in an item descriptor was invalid. ACMS$_INVSUB Error The submitter ID was invalid. ACMS$_NOSUCH_PKG Error There is no such application defined. ACMS$_NOSUCH_PROC Error There is no such procedure defined. ACMS$_NTSNIN Error Submitter was not signed in. ACMS$_SIGNOUT_ACTIVE Error A sign-out is active. ACMS$_SYNASTLVL Error Synchronous services may not be called from AST level. ACMS$_USERMODE Error This service must be called from user mode.
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