DELETE PROCEDURE statement

Deletes an instance of a persistent procedure. The persistent procedure can be local or remote.

Syntax

DELETE PROCEDURE proc-handle[ NO-ERROR ]

proc-handle

The handle of a local or remote persistent procedure. This is a variable, field, or expression of type HANDLE that contains a valid persistent procedure handle.

For a proxy procedure handle, this statement deletes the handle immediately unless there is an outstanding asynchronous request on this handle (handle:ASYNC-REQUEST-COUNT is greater than zero (0)). If handle:ASYNC-REQUEST-COUNT is greater than zero (0), this statement raises the ERROR condition. Otherwise, the statement also sends a request to the AppServer to delete the corresponding remote persistent procedure on the AppServer. If the AppServer is executing any asynchronous requests ahead of it, the AVM queues the delete request (as with any asynchronous remote request) until the AppServer is available to handle it.

Note: This same behavior occurs if the remote procedure deletes itself (using DELETE...THIS-PROCEDURE) on the AppServer.

For more information on remote persistent procedures, see OpenEdge Application Server: Developing AppServer Applications.

NO-ERROR

Suppresses ABL errors or error messages that would otherwise occur and diverts them to the ERROR-STATUS system handle. If an error occurs, the action of the statement is not done and execution continues with the next statement. If the statement fails, any persistent side-effects of the statement are backed out. If the statement includes an expression that contains other executable elements, like methods, the work performed by these elements may or may not be done, depending on the order the AVM resolves the expression elements and the occurrence of the error.

To check for errors after a statement that uses the NO-ERROR option:

• Check the ERROR-STATUS:ERROR attribute to see if the AVM raised the ERROR condition.
• Check if the ERROR-STATUS:NUM-MESSAGES attribute is greater than zero to see if the AVM generated error messages. ABL handle methods used in a block without a CATCH end block treat errors as warnings and do not raise ERROR, do not set the ERROR-STATUS:ERROR attribute, but do add messages to the ERROR-STATUS system handle. Therefore, this test is the better test for code using handle methods without CATCH end blocks. ABL handle methods used in a block with a CATCH end block raise ERROR and add messages to the error object generated by the AVM. In this case, the AVM does not update the ERROR-STATUS system handle.
• Use ERROR-STATUS:GET-MESSAGE( message-num ) to retrieve a particular message, where message-num is 1 for the first message.

If the statement does not include the NO-ERROR option, you can use a CATCH end block to handle errors raised by the statement.

Some other important usage notes on the NO-ERROR option:

• NO-ERROR does not suppress errors that raise the STOP or QUIT condition.
• A CATCH statement, which introduces a CATCH end block, is analogous to a NO-ERROR option in that it also suppresses errors, but it does so for an entire block of code. It is different in that the error messages are contained in a class-based error object (generated by the AVM or explicitly thrown), as opposed to the ERROR-STATUS system handle. Also, if errors raised in the block are not handled by a compatible CATCH block, ON ERROR phrase, or UNDO statement, then the error is not suppressed, but handled with the default error processing for that block type.
• When a statement contains the NO-ERROR option and resides in a block with a CATCH end block, the NO-ERROR option takes precedence over the CATCH block. That is, an error raised on the statement with the NO-ERROR option will not be handled by a compatible CATCH end block. The error is redirected to the ERROR-STATUS system handle as normal.
• If an error object is thrown to a statement that includes the NO-ERROR option, then the information and messages in the error object will be used to set the ERROR-STATUS system handle. This interoperability feature is important for those integrating code that uses the traditional NO-ERROR technique with the newer, structured error handling that features error objects and CATCH end blocks.

Example

When you run the following procedure non-persistently, the procedure creates a persistent instance of itself in addition to the non-persistent instance, creating two query windows for the Customer table. Choosing the Cancel button in either window causes the instance that owns that window to terminate. If the instance you terminate is persistent, the Cancel button runs an internal procedure that executes the DELETE PROCEDURE statement for that instance as specified by the THIS-PROCEDURE system handle.

r-delprc.p

DEFINE QUERY custq FOR Customer.
DEFINE BROWSE custb QUERY custq
  DISPLAY name balance phone WITH 10 DOWN.
DEFINE BUTTON bName LABEL "Query on Name".
DEFINE BUTTON bBalance LABEL "Query on Balance".
DEFINE BUTTON bCancel LABEL "Cancel".
DEFINE FRAME CustFrame custb SKIP bName bBalance bCancel.
DEFINE VARIABLE custwin AS HANDLE.

ON CHOOSE OF bName IN FRAME CustFrame DO:
  custwin:TITLE = "Customers by Name".
  OPEN QUERY custq FOR EACH Customer BY Customer.Name.
END.

ON CHOOSE OF bBalance IN FRAME CustFrame DO:
  custwin:TITLE = "Customers by Balance".
  OPEN QUERY custq FOR EACH Customer BY Customer.Balance DESCENDING.
END.

IF THIS-PROCEDURE:PERSISTENT THEN DO:
  THIS-PROCEDURE:PRIVATE-DATA = "Customer Browse".
  CREATE WIDGET-POOL.
END.

CREATE WINDOW custwin ASSIGN
  TITLE            = IF THIS-PROCEDURE:PERSISTENT THEN
    "Persistent Customer Browser" ELSE "Customer Browser"
  SCROLL-BARS      = FALSE
  MAX-HEIGHT-CHARS = FRAME CustFrame:HEIGHT-CHARS
  MAX-WIDTH-CHARS  = FRAME CustFrame:WIDTH-CHARS.

THIS-PROCEDURE:CURRENT-WINDOW = custwin.
ENABLE ALL WITH FRAME CustFrame.
IF THIS-PROCEDURE:PERSISTENT THEN DO:
  ON CHOOSE OF bCancel IN FRAME CustFrame DO:
    RUN destroy-query.
  END.
END.
ELSE DO:
  RUN r-delprc.p PERSISTENT. 
  WAIT-FOR CHOOSE OF bCancel IN FRAME CustFrame.
  DELETE WIDGET custwin.
END.

PROCEDURE destroy-query:
  DELETE PROCEDURE THIS-PROCEDURE.
  DELETE WIDGET-POOL.
END PROCEDURE.

Notes

• To be valid for deletion, proc-handle must reference an active persistent procedure. You can use the VALID-HANDLE function and PERSISTENT procedure attribute to check the validity of proc-handle. Thus, both VALID-HANDLE(proc-handle) and proc-handle:PERSISTENT must be TRUE to delete the specified procedure. If either of these expressions is FALSE, the DELETE PROCEDURE statement raises the ERROR condition.
• When you delete a persistent procedure instance, its context goes out of scope and all allocated resources are returned to the system. In addition, it is removed from the chain of persistent procedures referenced by the FIRST-PROCEDURE and LAST-PROCEDURE attributes of the SESSION system handle.
• If you delete a persistent procedure instance while executing statements within that procedure, the DELETE PROCEDURE statement pends until the largest executing block in the persistent procedure terminates. Thus, if the DELETE PROCEDURE occurs while the main procedure block is executing (when the persistent procedure is called), the procedure is deleted when the procedure returns (as if it were non-persistent). If the DELETE PROCEDURE occurs during execution of a trigger or execution of an internal procedure that is called from another external procedure, the procedure is deleted after the trigger block or internal procedure returns. Note that while the delete is pending, the persistent procedure remains valid in the persistent procedure chain.
• The DELETE PROCEDURE statement will only delete the proxy handle on the client of a procedure run as single-run or singleton. This is because the AVM automatically deletes a single-run procedure after execution, and a singleton procedure may be running on multiple AppServer agents.
• The DELETE PROCEDURE statement disconnects any local buffers established by the procedure. In addition, any buffers passed as parameters to a persistent procedure are treated as local buffers. While all cursor positioning established on these buffers by the persistent procedure is lost, there is no affect on the original buffers passed as parameters from the caller. Note that all buffers are validated before being disconnected (which might cause database write triggers to execute). If the validation fails, the DELETE PROCEDURE statement raises the ERROR condition and pends the deletion until the validation succeeds and all database write triggers have completed.
• For more information on working with asynchronous remote procedures and event procedures, see OpenEdge Application Server: Developing AppServer Applications.

See also

RUN statement, THIS-PROCEDURE system handle, VALID-HANDLE function