How Can I Find Mandatory...

Hi All,

i have done IDOC to File scenario . where i have choosen basic type as delfor02. in xi server i created data types such as IDOC,DELFOR02,etc.... in this scenario i have screen shots so i done. but assume that i am using some other basic type say for example PEXR2002.

now this basic type i need to create data type which are mandatores to make mapping is it .

my question is how can i find mandatory segments for PEXR2002 or some other.

please tell me find because i just start XI.

regards,

Selva.