Input of Null-Capable Fields

For a field that is null-capable in the RPG program, the following will apply on input, for DISK, SEQ, WORKSTN and SPECIAL files:

• When a null-capable field is read from an externally described file, the null indicator for the field is set on if the field is null in the record. Otherwise, the null indicator is set off.
• If field indicators are specified and the null-capable field is null, all the field indicators will be set off.
• If a field is defined as null-capable in one file, and not null-capable in another, then the field will be considered null-capable in the RPG program. However, when you read the second file, the null indicator associated with the field will always be set off.
• An input operation from a program-described file using a data structure in the result field does not affect the null indicator associated with the data structure or any of its subfields.
• Reading null-capable fields using input specifications for program-described files always sets off the associated null indicators.
• If null-capable fields are not selected to be read due to a field-record-relation indicator, the associated null indicator will not be changed.
• When a record format or file with null-capable fields is used on an input operation (READ, READP, READE, READPE, CHAIN) and a data structure is coded in the result field, the values of %NULLIND for null-capable data structure subfields will be changed by the operation. The values of %NULLIND will not be set for the input fields for the file, unless the input fields happen to be the subfields used in the input operation.

Null-capable fields cannot be used as match fields or control-level fields.