Deactivate the Generate log data option if you do not want warning and error information written to the log. However, if you do deactivate this option, the FBX Exporter/Importer does not write log data (such as errors and warnings,) to the generated log file. However, the file name and time stamp are still recorded in the log.
The Maya FBX Plug-in stores log files with the FBX presets, in C:\My Documents\Maya\FBX\Logs.
Log files are important for tracking errors and warnings on export. It is not recommended to deactivate this option when you export a series of files, for example, in an automation or batch export because you will not receive any feedback about any issues that concern files during export. This lack of feedback can make it difficult to identify problem files which, in turn, makes diagnosing problems difficult.