I run it gather schema statistics using concurrent program. It successfully completed. But when when i click output ,It showing "the output file for request is empty " . I just want to know What is my next step? Why output doesn't come?
No further action is required and as long as the concurrent program complete successfully then you should be good.
Please see (How to Determine When a Table Was Last Analyzed By the Gather Schema Statistics Program (Doc ID 166346.1)).