$RRN Function

The $RRN function is used with VSAM RRDS files to access a specific record or range of records. This function returns the current relative record number at each iteration of the FOR construct. You can use the $RRN function in the WHERE clause of a FOR statement, as the source operand in SET statements, and in expressions.

This function has the following format:

$RRN[(dataview‑name)]

dataview‑name: The name of a VSAM dataview that defines an RRDS file. The dataview name is required for this function, except when the function is used in a WHERE clause. You cannot specify the dataview name for this function in the WHERE clause.

You cannot set the value of the $RRN function , therefore, you cannot use the $RRN function as the target of a SET or MOVE statement.
The $RRN function is accessible only when the dataview fields are accessible. You cannot use this function before the execution of a FOR statement.
When adding records to an RRDS file, the WHERE clause is required and the $RRN function is used as the left operand of the WHERE clause. The operator must be equal to (=) and the right operand can be an integer number, a numeric expression, or a numeric data item or field.
The first record of an RRDS file has a relative record number of 1.

Examples

In the following example, the $RRN function is used in the WHERE clause in a FOR NEW statement to add records in consecutive slots in an RRDS file named PAYROLL. To find the last record in the existing file, a FOR FIRST construct is used with an ORDERED BY DESCENDING clause. The working data field NEXT‑REC is set by adding 1 to the number the $RRN function returns.

FOR FIRST PAYROLL
   ORDERED BY DESCENDING
        SET NEXT‑REC = $RRN(PAYROLL) + 1
WHEN NONE
        SET NEXT‑REC = 1

ENDFOR

FOR NEW PAYROLL
    WHERE $RRN = NEXT‑REC
        statements
        SET NEXT‑REC = $RRN(PAYROLL) + 1
ENDFOR

In the next example, the $RRN function finds a specific record in the PAYROLL file.

FOR FIRST PAYROLL
    WHERE $RRN = 6
        statements
ENDFOR