General syntax of DEFINE DATA CONTEXT:
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CONTEXT |
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USING |
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local-data-area |
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| parameter-data-area | |||||||||
context-data-definition
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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
The DEFINE DATA CONTEXT statement is used in conjunction
with the Natural Remote
Procedure Call (RPC). 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 programming objects executed in one conversation that refer to that name. The variable is allocated by the first executed programming object that contains the definition of the variable and is deallocated when the conversation ends.
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 but the variables can be shared
with all its callees.
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.
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 Remote Procedure Call (RPC) documentation.
A context variable must be defined at Level 01. Other levels are only used in a redefinition.
| USING local-data-area |
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 DEFINE DATA CONTEXT USING DATX_L CONTEXT USING DATX_P ... END-DEFINE ; For further information, see also Defining Fields in a Separate Data Area in the Programming Guide. |
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| USING parameter-data-area | A parameter data area contains data elements which are used as parameters in a subprogram, external subroutine or dialog. |
| 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 | The Natural reserved word END-DEFINE must be used
to end the DEFINE DATA statement.
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Context data can be defined directly within a program or routine. For direct data definition, the following syntax applies:
| level |
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variable-definition |
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| redefinition | |||
| handle-definition |
For further information, see Defining Fields within a DEFINE DATA Statement in the Programming Guide.
| level | An application-independent variable must be defined at Level 01. Other levels are only used in a redefinition. |
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| variable-definition |
A variable-definition is used to define a single field/variable that may be single-valued (scalar) or multi-valued (array). See Variable Definition. Note: |
| 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). See Redefinition. |
| handle-definition | A handle identifies a dialog element in code and is stored in handle variables. See Handle Definition. |
Note:
The fields resulting from the redefinition are not considered a
context variable. These fields are treated as local variables.
