Specify the key field (example 3)

In this example, consider a logical employee file over five physical files.

Figure 1. Specify the key field (example 3)

|...+....1....+....2....+....3....+....4....+....5....+....6....+....7....+....8
00010A          R EMPMST                    PFILE(EMPMSTP)
00020A          K EMPNBR  1
00030A*
00040A          R CLSREG                    PFILE(CLSREGP)
00050A          K EMPNBR  1
00060A          K CLSDTE  2
00070A*
00080A          R CLSHST                    PFILE(CLSHSTP)
00090A          K EMPNBR  1
00100A          K CLSDTE  2
00110A*
00120A          R JOBHST                    PFILE(JOBHSTP)
00130A          K EMPNBR  1
00140A          K *NONE   2
00150A          K JOBDTE  3
00160A*
00170A          R ACTHST                    PFILE(ACTHSTP)
00180A          K EMPNBR  1
00190A          K *NONE   2
00200A          K ACTDTE  3
     A

Record format	Key positions
	1	2	3
EMPMST	EMPNBR	*NONE	*NONE
CLSREG	EMPNBR	CLSDTE	*NONE
CLSHST	EMPNBR	CLSDTE	*NONE
JOBHST	EMPNBR	*NONE	JOBDTE
ACTHST	EMPNBR	*NONE	ACTDTE

The records are merged and sequenced as follows:

All records are merged and sequenced by employee number.
For a given employee, records are sequenced by:
1. The master record (of the EMPMST format)
2. Records of the CLSREG and CLSHST formats, merged and sequenced together on values of CLSDTE (key position 2)
3. Records of the JOBHST and ACTHST formats, merged together and sequenced together on values of JOBDTE and ACTDTE (key position 3)

Specifying *NONE in the key definitions achieves this sequencing as follows:

*NONE and a field name, CLSDTE, appear in the second key position of the adjacent formats, CLSHST and JOBHST. This effectively causes a split between the two formats after the preceding key position (position 1). Records of formats above the split are merged and sequenced with records of formats below the split only on values of EMPNBR.
An implicit *NONE in the second key position of the format EMPMST forces a similar split.
With *NONE in key position 2, the JOBHST and ACTHST formats form a set in which the values of JOBDTE and ACTDTE are compared in order to merge and sequence records of these two formats only.

The record sequence defined by the previous key specifications is totally dependent on the order in which the formats are specified. For example, if JOBHST is specified before CLSHST, key position 2 will read:

*NONE, CLSDTE, *NONE, CLSDTE, *NONE

Here, the values of CLSDTE within CLSREG will not be sequenced with the values of CLSDTE within CLSHST, and JOBDTE will not be sequenced with ACTDTE.