Do not edit the control file. You might inadvertently corrupt it. Regardless of the editor you use, do not open and then save this file.
This is true especially if Historical Server is running on Windows NT. Unlike the other files created by Historical Server, the control file is not a standard-format Windows NT text file. Lines of text in the control file are terminated only with newline characters, rather than the usual carriage-return/newline pairs. Do not try to edit this file because the editing program may corrupt the file by embedding unwanted carriage-return/newline pairs into the text.