Do I need second master's degree or not? I finished master's degree in "System analysis and management" (Engeenering). I have Bachelor's in Computer Science. Can I enroll to PhD in Computer Science now and change field research? Or me need enroll to Master's again (in Computer Science) for changing scientific research? 

P.S. I'm going to enroll German or Austrian PhD.
There is usually not a formal requirement for PhD candidates to have a master's degree in the subject of their PhD. Indeed, having a master's degree from a field different to that of the PhD is very common in some disciplines.

The main thing to bear in mind is that applicants for a PhD programme must convince the admissions committee that they have the skills and academic potential that will be necessary to successfully complete the programme. When completing your PhD application, think about the kinds of skills and background knowledge that will be important for your PhD and explain why you have those skills, or why the admissions committee should believe that you are able to quickly acquire them