I am unfamiliar with answering your DI-specific question about how/where to introduce the "??" parameter for "file reader" - possibly. Are you getting a SAS ERROR or a NOTE/WARNING message when you run your program with INFORMAT s370fpd6. specified?
Check the SAS Language Elements discussion on the INPUT statement and using INFORMATs - particularly, the topic on INVALID DATA. The only relief it provides is to mask the condition in the SAS log, suppressing the warning message. Consider though (I believe) you still end up with the desired result, a SAS numeric variable with a missing value condition.
Possibly there may be information here (or you may need to contact SAS tech support for guidance) - or just ignore the SAS log warning messages about INVALID DATA or INVALID ARGUMENT TO FUNCTION:
http://support.sas.com/documentation/cdl/en/etlug/60948/HTML/default/p0rhnqjrb6tje9n1jyfk9h4kn386.ht...
Scott Barry
SBBWorks, Inc.
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