Hi Kumari,
Judging from your context-less question, I assume you are an end-user and therefore not aware that the way SAP calculatea per diems etc. -ans whether per diems are created at all - is highgly configurable for each customer.
So, it is not possible to answer your question without far more context. Your first port of call should not be this forum, but the person, who has configured your system. Should they not be able to solve this, I recommend they put the question back here - they will be able to describe the problem and it's context in a way that the experts on the SCN have a chance of providing effective help