Hi Thanks for your suggession. But there is no file named '45xsession' in /etc/X11/Xsession.d/.

There is only 5 files named below

20xfree86-common_process-args
50xfree86-common_determine-startup
99xfree86-common_start
30xfree86-common_xresources
90xfree86-common_ssh-agent

regards.