Google： msb files are Oracle message files, binary version. Whenever you get an error like ORA-1234 or IMP-123, relevant message files are read and the errors are fetched. These files are always open by Oracle processes (threads in windows).In UNIX, you have msg files in addition to msb. But msg files are never used by Oracle processes. They're there only for humans to read and used by the oerr utility. They contain the same information as their msb counterpart.
msb files are Oracle message files, binary version. Whenever you get an error like ORA-1234 or IMP-123, relevant message files are read and the errors are fetched. These files are always open by Oracle processes (threads in windows).In UNIX, you have msg files in addition to msb. But msg files are never used by Oracle processes. They're there only for humans to read and used by the oerr utility. They contain the same information as their msb counterpart.