For mainframe files we usually suggest to use Power Exchnage to read the EBCIDIC data. As Power Exchange internally takes care of the data format. Copybook is required for creating a datamap that will being used by power exchnage to read.
If you do not have the copybook, atleast you should know the structure of the file so that you can add manually.
like for fixed byte, we might add one field having complete record.
For Variable, we should know the different record types and then add different records as per the length of the file.
Please refer KB article for detailed steps : https://kb.informatica.com/howto/6/Pages/2/157664.aspx
Also i would request to open a case with Informatica Power Exchnage team and provide file details (DCB parameter) , sample file and we can do a sample test and provide you more information.
If you have neither a copybook nor nay layout description, then you MAY be able to analyse these files piece by piece using the PowerExchange Navigator (the 64-bit Windows client tool).
However, this is a daunting task and extremely error-prone. Have fun, I only can say, if there's no alternative approach available for you.
Good luck and regards,
PowerExchange has no innate ability to identify the contents of a file and create an appropriate datamap.
Given the existence of multiple record formats in any given file, that would be a pretty much impossible task.
You will need to do the data discovery work on your own, outside of Informatica, and create appropriate COBOL Copybooks to reference the record formats.