Defining Context Variables for Natural RPC

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# 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
`END-DEFINE`

This document covers the following topics:

- Function

- Restrictions

- Syntax Description

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 Natural objects except subprograms executed by this non-conversational `CALLNAT`.

The optional `INIT` clause is evaluated in each executed Natural object that contains this clause (not only in the Natural 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 context 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 context data definition, the following syntax applies:

level |  | variable-definition |
redefinition

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.

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

### On this page

- Function
- Restrictions
- Syntax Description