Multiple process writing on same file problem.

Muliple process access to writing on same file simultaneously..if the file size is excess on the limit(example 10mb),the processing file is renamed(rolling appender) and create a new one on the same file name and writting process is working continuously. My issue is ,multiple process is running at same time,if one of the process is still writing on the file then i can't rename that file.how to resolve that problem.