Example of DFHNCTR calls with null parameters

If you omit an optional parameter on a DFHNCTR call, ensure that the parameter list is built with a null address for the missing parameter. The example that follows illustrates how to issue, from a COBOL program, an NC_CREATE request with some parameters set to null addresses.

DFHNCTR call with null addresses for omitted parameters: In this example, the parameters that are used on the call are defined in the WORKING-STORAGE SECTION, as follows:

Call parameter	COBOL variable	Field definition
function	01 NC-FUNCTION	PIC S9(8) COMP VALUE +1.
return_code	01 NC-RETURN-CODE.	PIC S9(8) COMP VALUE +0.
pool_selector	01 NC-POOL-SELECTOR	PIC X(8).
counter_name	01 NC-COUNTER-NAME	PIC X(16).
value_length	01 NC-VALUE-LENGTH	PIC S9(8) COMP VALUE +4.
current_value	01 NC-CURRENT-VALUE	PIC S9(8) VALUE +0.
minimum_value	01 NC-MIN-VALUE	PIC S9(8) VALUE +0.
maximum_value	01 NC-MAX-VALUE	PIC S9(8) VALUE -1.
counter_options	01 NC-OPTIONS	PIC S9(8) COMP VALUE +0.
update_value	01 NC-UPDATE-VALUE	PIC S9(8) VALUE +1.
compare_min	01 NC-COMP-MIN	PIC S9(8) VALUE +0.
compare_max	01 NC-COMP-MAX	PIC S9(8) VALUE +0.

The variable that is used for the null address is defined in the LINKAGE SECTION, as follows:

LINKAGE SECTION.
01 NULL-PTR USAGE IS POINTER.

Using the data names that are specified in the WORKING-STORAGE SECTION as described, and the NULL-PTR name as described in the LINKAGE SECTION, the following example illustrates a call to a named counter-server where value_length, current_value, minimum_value and counter_options are the only optional parameters specified. The others are allowed to default, or, in the case of trailing optional parameters, omitted altogether.

 NAMED-COUNTER SECTION.
*
SET ADDRESS OF NULL-PTR TO NULLS.
*
MOVE 1 TO NC-FUNCTION.
MOVE 100 TO NC-MIN-VALUE NC-CURRENT-VALUE.
MOVE NC-WRAP TO NC-OPTIONS.
MOVE "DFHNC001" TO NC-POOL-SELECTOR.
MOVE "CUSTOMER_NUMBER" TO NC-COUNTER-NAME.
CALL 'DFHNCTR' USING NC-FUNCTION NC-RETURN-CODE NC-POOL-SELECTOR
NC-COUNTER-NAME NC-VALUE-LENGTH NC-CURRENT-VALUE
NC-MIN-VALUE NULL-PTR NC-OPTIONS.

If you want to use DCOUNTER instead of COUNTER with DFHNCTR, then you need to change the NC-CURRENT-VALUE, and the NC-MIN-VALUE and NC-MAX-VALUE definitions from signed decimal values (as previously listed) to unsigned doubleword binary definitions, for example PIC 9(16) COMP. Also, MOVE 8 to NC-VALUE-LENGTH.