Selection Processing

The selection process compares the intermediate format of file data against the intermediate format of input data.

Processing

The processing steps are as follows:

1. Input data in selection clause
2. Input conversion processing of input data
3. Input value in intermediate format
4. File data in stored format
5. Attribute 8 processing of file data
6. File data in intermediate format
7. Comparison of the two values in their intermediate format.

Input Versus Output Conversion

An input conversion may be different from an output conversion.

Some codes, for example D (date conversion), are automatically invertable, that is, the output conversion code is the same as the input conversion code. The processor simply performs the inverse of the output conversion if input data is being transformed.

Some codes, such as T (translate), have different specifications for input and output conversions. You must set up the translate data to accommodate both conversions.

Some codes, such as C (concatenate), are not invertable, but you can specify them for input conversion. However, they do not invert the data: they simply perform an output conversion on the input data.

The function codes A, AE, F, FE, and FS are not invertable, and cannot be specified for input processing.