Defining Context Variables for Natural RPC

General syntax of DEFINE DATA CONTEXT:

DEFINE DATA
   CONTEXT

USING

local-data-area

 
parameter-data-area
context-data-definition ../graphics/dot3.gif

END-DEFINE  

This document covers the following topics:

For an explanation of the symbols used in the syntax diagrams, see Syntax Symbols.

Belongs to Function Group: Natural Remote Procedure Call

Function

The DEFINE DATA CONTEXT statement is used in conjunction with the Natural RPC (Remote Procedure Call). It is used to define variables known as context variables, which are meant to be available to multiple remote subprograms within one conversation, without having to explicitly pass the variables as parameters with the corresponding CALLNAT statements.

A context variable is referenced by its name, and its content is shared by all Natural objects executed in one conversation that refer to that name. The variable is allocated by the first executed Natural object that contains the definition of the variable and is deallocated when the conversation ends.

A context variable is not shared with subprograms that are called within the conversation. If such a subprogram or one of its callees references a context variable, a separate storage area is allocated for this variable.

Context variables can also be used in a non-conversational CALLNAT. In this case, the context variables only exist during a single invocation of this CALLNAT. The variable is allocated when the remote subprogram is started and deallocated when it ends. The content is shared by all programming objects except subprograms executed by this non-conversational CALLNAT.

The optional INIT clause is evaluated in each executed programming object that contains this clause (not only in the programming object that allocates the variable). This is different to the way the INIT works for global variables.

For further information, see Defining a Conversation Context in the Natural RPC (Remote Procedure Call) documentation.

Restrictions

A context variable must be defined at Level 01. Other levels are only used in a redefinition.

Syntax Description

Syntax Element Description
USING local-data-area
LDA Name:

A local data area (LDA) contains data elements which are to be used in a single Natural module. You may reference more than one data area; in that case you have to repeat the reserved words CONTEXT and USING, for example: 

DEFINE DATA
  CONTEXT USING DATX_L
  CONTEXT USING DATX_P

  ...
END-DEFINE ;

For further information, see Defining Fields in a Separate Data Area in the Programming Guide.

USING parameter-data-area
PDA Name:

A parameter data area contains data elements which are used as parameters in a subprogram, external subroutine or dialog.

context-data-definition
Context Data Definition:

Context data can be defined directly within a program or routine. For direct data definition, the syntax shown below applies.

END-DEFINE
End of DEFINE DATA Statement:

The Natural reserved word END-DEFINE must be used to end the DEFINE DATA statement.

Context Data Definition

Context data can be defined directly within a program or routine. For direct data definition, the following syntax applies:

level

variable-definition

redefinition
handle-definition

For further information, see Defining Fields within a DEFINE DATA Statement in the Programming Guide.

Syntax Element Description
level
Level Number:

An application-independent variable must be defined at Level 01. Other levels are only used in a redefinition.

variable-definition
Variable Definition:

A variable-definition is used to define a single field/variable that may be single-valued (scalar) or multi-valued (array).

For further information, see Variable Definition.

Note:
The CONSTANT clause must not be used in this context

redefinition
Redefinition:

A redefinition may be used to redefine a group, a view, a DDM field or a single field/variable (that is a scalar or an array).

For further information, see Redefinition.

handle-definition
Handle Definition:

A handle identifies a dialog element in code and is stored in handle variables.

Note:
The fields resulting from the redefinition are not considered a context variable. These fields are treated as local variables.