Modifying fields in the command-level parameter structure

Some fields that are passed to transient data are used as input to the request, some are used as output fields, and some are used for both input and output. The method your user exit program uses to modify a field depends on the usage of the field.

LENGTH is an input field on a WRITEQ request, and an output field on a READQ request that specifies SET. It is both an input and an output field on a READQ request that specifies INTO.