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Control file
Header record
User's Guide
The hs.ctl control file resides in the Historical Server home directory. The
control file maintains information about all recording sessions, past and
present, known to Historical Server. See "The Historical Server control file
and home directory" on page 9 for more details about how Historical Server
uses the control file.
Use the Historical Server
the Historical Server control file. Do not edit the control file. You might
inadvertently corrupt the file.
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
new-line characters, rather than the usual carriage-return/newline pairs. The
editing program may corrupt the file by embedding unwanted carriage-
return/newline pairs into the text.
The control file contains the following types of records:
•
Header record
•
Session control record
•
Data item control record
•
Alarm control record
•
View control record
•
Filter control record
The first record in the control file is a header record that contains the following
six integer fields:
•
An "update in progress" flag
•
A byte offset in the file of the information being updated
•
A unique session ID to be assigned by Historical Server to the next
recording session
•
A copy of the unique session ID for use in file corruption detection and
recovery
command to gain access to the information in
hs_list
CHAPTER 5
Data Files
91
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