Hello Nivash,
"At the time open text sends the completed letter to the Filenet repository I need to store some metadata about that file, like the File name, created time, etc... how can I get this information from Open Text?" - I guess the stored document from OTAS will be used to create the letter through template which means the info is already available in the OTAS DB(not sure where to get filename from, within DB. Other info should be available in "ds_doc" table of the DB if I still remember it correctly) .
"But how can I send data to Open Text is it through any RFC function modules or some XML formats. Or is there a entirely different strategy involved in that. Please let me know." - I see that only once the data is being send to OpenText, which will be handled by the configurations which I already specified. If you are asking what's happening background partly YES to RFC FM.
Hope this helps you
Good Day!
Kolusu