Select or omit field name

Use select or omit fields to tell the operating system how to select or omit records when your program retrieves them using this record format. The only records affected are those from the physical file(s) specified for the PFILE or JFILE keyword for this record format.

The following rules apply to select/omit fields in logical files:

You can specify select/omit fields only if you also specify key fields or if you also specify the DYNSLT keyword for the file. You can also specify *NONE as a key field to satisfy the requirement for a key field when your application requires no key fields.
For simple and multiple-format logical files, the operating system uses the following search order to match select/omit field names with defined fields:
- Fields specified in DDS positions 19 through 28
- Fields specified as parameters on the CONCAT or RENAME keyword
If the field name is specified more than once, the first occurrence is used.

The field name on a CONCAT or RENAME keyword and the associated field name in positions 19 through 28 cannot both be specified as select/omit fields.

The parameter name on the SST keyword is not valid as a select/omit field unless it is defined elsewhere in the logical file record format.

For join logical files, the select/omit field name you specify must be specified at the field level in positions 19 through 28.

When using the select/omit fields, specify either S or O in position 17. By specifying either S or O, the select and omit comparison statements are grouped by OR. The system treats the select and omit comparison statements that are grouped by OR independently from one another. That is, if the select or omit comparison condition is met, the record is either selected or omitted. If the condition is not met, the system proceeds to the next comparison.

By specifying a blank in position 17, the select and omit comparison statements are ANDed together. The combined comparisons must be met before the record is selected or omitted. See Figure 1 and Figure 2. In positions 19 through 28, specify a field name whose contents at processing time determine whether the record is to be selected or omitted based on the select/omit keyword specified for this field. The select/omit keywords are COMP, RANGE, and VALUES. The last select/omit specification can be made with the ALL keyword, but a field name is not permitted.

The field must appear in both the physical file record format and the logical file record format. Select/omit statements must follow all field and key field level entries for the record format. You can specify both select and omit for the same record format. The following information applies:

If you specify both select and omit for a record format, the order in which you specify them is important.
The select/omit statements are processed in the order they are specified; if a record satisfies a statement, the record is either selected or omitted as specified, and remaining select/omit statements are not examined for that record. See Figure 3
.
If you specify both select and omit statements, you can indicate whether records not meeting any of the values specified are to be selected or omitted.
If you do not specify the ALL keyword, the action taken for the records that do not meet the values is the converse of the type of the last statement specified. Records that do not meet selection values are omitted, and records that do not meet omission values are selected.

There are limits to the number of select/omit statements you can specify in a single logical file. If you specify many select/omit statements and you cannot create the file, reduce the overhead for the file through the following changes in the specifications, in decreasing order of importance:

Reduce the number of record formats in the file.
Reduce the number of physical files specified on the PFILE or JFILE keyword.
Reduce the number of fields used (single occurrences) in the select/omit specifications.

You cannot specify a floating-point field as a select/omit field.

It is possible to have an access path with select/omit and process the file in arrival sequence. For example, CPYF can be specified with FROMRCD(1) or the high-level language cannot request keyed processing. In this case, the processing is the same as if the DYNSLT keyword had been specified.

Figure 1 shows how to specify the select/omit field using select statements that are grouped by AND.

Figure 1. Specify the Select/Omit field (example 1)

|...+....1....+....2....+....3....+....4....+....5....+....6....+....7....+....8
00010A          R RECORD1                   PFILE(PARTS)
00020A            PNO
00030A            DSC
00040A            UPR
00050A            QOH
00060A          K PNO
00070A          S UPR                       COMP(GT 5.00)
00080A            QOH                       COMP(LT 10)
00090A          O                           ALL
     A

In Figure 1, records are selected only if they satisfy two select statements: the first statement selects records in which the value of field UPR is greater than 5.00, and the second statement selects records in which the value of field QOH is less than 10. S is not specified in position 17 for field QOH. Therefore, these select statements are grouped by AND. For a record to be read by a program, both conditions specified must be true.

Figure 2 shows how to specify the select/omit field using an omit statement that is grouped by OR with two select statements that are grouped by AND.

Figure 2. Specify the Select/Omit field (example 2)

|...+....1....+....2....+....3....+....4....+....5....+....6....+....7....+....8
00010A          R RECORD1                   PFILE(PARTS)
00020A            PNO
00030A            DSC
00040A            UPR
00050A            QOH
00060A          K PNO
00070A          O DSC                       COMP(EQ 'HAMMER')
00080A          S UPR                       COMP(GT 5.00)
00090A            QOH                       COMP(LT 10)
00100A          O                           ALL
     A

In Figure 2, records are supplied to the program if they pass both of the following tests:

The DSC field is not equal to HAMMER.
The UPR field is greater than 5.00 and the QOH field is less than 10.

Figure 3 shows several ways to specify the same select/omit logic.

Figure 3. Specify the Select/Omit field (example 3)

|...+....1....+....2....+....3....+....4....+....5....+....6....+....7....+....8
00010A          S ST                        COMP(EQ 'NY')
00020A            REP                       COMP(EQ 'JSMITH')  1
00030A            YEAR                      COMP(LT 78)
00040A          O                           ALL
     A
00050A          O YEAR                      COMP(GE 78)
00060A          S ST                        COMP(EQ 'NY')      2
00070A            REP                       COMP(EQ 'JSMITH')
00080A          O                           ALL
     A
00090A          O REP                       COMP(NE 'JSMITH')
00100A          O ST                        COMP(NE 'NY')      3
00110A          S YEAR                      COMP(LT 78)
00120A          O                           ALL
     A

In Figure 3, you want to select all the records before 1978 for a marketing representative named JSMITH in the state of New York. There are three ways to code this example:

All records must be compared with the select fields ST, REP, and YEAR before they can be selected or omitted.
All records in and after 1978 are omitted in the first comparison. Then, only the records before 1978 are compared with ST and REP. Only two select fields must be satisfied. This way is more efficient than method 1.
All records that are not associated with JSMITH in the state of New York are omitted in the first and second comparisons. Then, all records left are compared to YEAR. This is more efficient than method 1 or method 2.