Trace File Location for pl/sql Sessions

You can get information from here

Trace file name is generated using function FND_DEBUG_UTIL.get_trace_file_name. Depending upon platform such as LINUX, AIX, WIN_NT, HP, trace file name can vary a little bit.

I think system/session parameter "tracefile_identifier" can be set in oracle application. At my site it is set to user id. It makes it easier to locate trace files generated by a particular user. No need to look for session id etc.