# Perf Data Log Overview
The Perf Data Log utility consists of two components:
•	The Configuration property pages
•	The Data Collection service
The configuration property pages are used to configure the operation of the data collection service. The data collection services can also be started and stopped by the configuration property pages as well.
Features
The Perf Data Log utility is a service that runs in the background on a Windows NT system to monitor and record performance data of selected system parameters. The performance data is recorded in a text format for easy manipulation by common database and spreadsheet applications. Since the utility runs as a service it can be started automatically when the system is started or controlled manually. The log files created by the service can be renamed periodically for subsequent manipulation or archiving.

Installation
The Perf Data Log service is installed by copying the following files the SYSTEM32 directory in the WINDOWS NT root directory. 
•	PDLCNFIG.EXE – The configuration program
•	PDLCNFIG.HLP – The configuration program help file 
•	PDLCNFIG.CNT – The configuration program contents file 
•	PDLSVC.EXE  – The data collection service
•	PDH.DLL – The performance data interface library
Once all these files are in place, the configuration program will install the service the first time it is run on the system.
Configuration
Before the data collection service can start logging data it must be configured using the Configuration property pages. The Configuration property pages are in the PDLCNFIG application program.
Log Settings
The Log Settings property page is used to select the performance counters to log and the interval between data samples. The service can also be started, stopped and set to automatic using this property page.
Log Files
This property page is used to configure how the data will be written. The output file can be named specifically, or it can be renamed periodically.
Operation
Once the service has been configured, it can be started by either selecting the Start button on the Log Settings page, or the service can be set to start automatically the next time the system is restarted. The data files generated by the service can be viewed while the service is running, so long as they are not locked, preventing possible updates by the service. If this may be a problem, then the service should be stopped while the files are read or copied.
Using the Data
The data from the data files is stored in a common text data format and may be imported into spreadsheet or database applications. (Microsoft Excel or Access, for example). Once in the database, the user may manipulate the data as desired.

# Log Settings
The Log Settings property page is used to configure the counters to be logged, the sample interval and the status of the logging service.
Service Start
The buttons in this group control the data collection service.
Automatic
Select this radio button to cause the service to start automatically each time the system is restarted
Manual
Select this radio button to cause the service to start and stop manually. The service can be controlled by the Start and Stop buttons in this group box or by the Services Control Panel applet.
Start
Select this button to start the data collection service. This button is only enabled when the Manual radio button is selected and the service is not currently running.
Stop
Select this button to stop the data collection service. This button is only enabled when the Manual radio button is selected and the service is currently running.
Sample Interval
These controls determine how often data is collected by the service. The sample interval should be as long as possible to minimize the load imposed by the data collection service. Samples can be as frequent as every second, to several days apart. The best interval will depend on the counters being monitored.
Counters
The counters that are currently selected for logging are displayed in this list box.
Add
Select this push button to display the performance counter browsing dialog box. The performance counters to log are selected from this dialog box and then displayed in the Counters list box, when the browser is closed.
Remove
This push button is used to remove the counters selected in the Counters list box. When this button is selected, all the selected counter entries in the list box will be removed.

# Log File
The Log File property page is used to configure the properties of the log file created by the data collection service.
Log File Format
The log file created by the data collection service can be formatted in one of  the two ways listed below. Select the one that is appropriate for the application to read or process the data after it has been collected.
Comma Separated Variable (.CSV) 
When this format is selected, the data will be written as values separated by a comma.
Tab Separated Variable (.TSV)
When this format is selected, the data will be written as values separated  by a tab character.
Manual Filename Assignment
Selecting this radio button will cause the data collected by the data collection service to be written to the file specified in the Output Filename edit box. NOTE: That if there is a file with this name already in existence, then the old file will be overwritten by the new file.
Output Filename
This edit box is used to enter the desired output file for the data collection service. The […] push button to the right of this edit box can be selected to use the file browser to select the output filename and directory path.
Automatic Filename Assignment
Selecting this radio button will cause the output file created by the data collection service to be renamed periodically. The renaming interval as well as the base name and output folder for the files can be configured by the fields in this box as well.
Rename output file every
These controls are used to configure the renaming interval of the output files. Enter the number of units directly into the edit box or use the arrows to adjust the number. The units are selected from the combo box next to the digits.
Log Folder…
This push button is used to select the folder that the log files are to be written to. Make sure there is sufficient disk space on the drive containing that folder as the service will terminate if  there is no longer enough room to write the data to the output file.
Base Filename
This edit control is used to specify the base file name or the left-most part of the filename. The filename used consists of the base filename followed by a sequence string specified by the Auto Format control. An example of the resulting filename is shown in the Example control at the bottom of this group.
Auto Format
This control is used to specify how the sequence string will be formatted. The letters in the string indicate data will be derived from the following :
nnnnnn = a decimal number that increases from 1 to 999,999 by 1 each time a new file is created
yy = the last two digits of the current year (1996 = 96)
mm = the two digits that describe the current month (Jan = 01)
dd = the two digits that describe the current day of the month
ddd = the 3 digit day of the current year (i.e. the Julian Date)
hh = the 2 digit hour of the day from 0 to 23 ( 5:00 pm = 17)
Example
In this control, an example of what an automatically generated name will look like using the current date and time.