Hi Sudheer,
you will find the answers to your questions in help from LabVIEW. Take a look in help Property and Method References>>VI Server>>Application>>Methods>>Mass Compile.
There you will find that LOGFILE "Specifies a file path where results of the mass compile should be placed. The default is no file." And for APPENDLOG you will find "Specifies whether results should be appended to the log file. The default is FALSE."
I hope this will help you.
Rebecca Fox
National Instruments
Rebecca Fox
Applications Engineer
National Instruments