Opening a Log File for Writing and Writing to the Log File

Open a log file for writing by calling PdhOpenLog and specifying a log file name as the szDataSource parameter. PdhOpenLog is used only to open a log file for a write operation.

Do the following to write to a log file:

1. Call PdhOpenQuery to establish the source of the performance data that will be written to the log file. This can be either a real-time source or a log file.
2. Call PdhOpenLog, passing in the handle to the query object created by the earlier call to PdhOpenQuery.
3. Update the query and collect the performance data from the data source by calling PdhUpdateLog.