Oracle Installation errors

Some time it happens that we could not start our Xwindow terminal from oracle user window, if we have su(switch user) from root user.
Like if we execute the following command we get the error

Bash-3.00$ cd clusterware
Bash-3.00$ ./runInstaller

Starting Oracle Universal Installer...
Checking installer requirements...
Checking operating system version: must be 5.10. Actual 5.10 Passed
Checking Temp space: must be greater than 250 MB. Actual 1982 MB Passed
Checking swap space: must be greater than 500 MB. Actual 2348 MB Passed
Checking monitor: must be configured to display at least 256 colors
>>> Could not execute auto check for display colors using command /usr/openwin/bin/xdpyinfo. Check if the DISPLAY variable is set. Failed <<<<
Some requirement checks failed. You must fulfill these requirements before
continuing with the installation,at which time they will be rechecked.
Continue? (y/n) [n] n

The solution to this problem is

As root user
Bash-3.00# export DISPLAY=192.168.235.111:0.0

Bash-3.00# su – oracle
Sun Microsystems Inc. SunOS 5.10 Generic January 2005
$ bash
Bash-3.00# export DISPLAY=192.168.235.111:0.0
Bash-3.00# echo $DISPLAY
192.168.235.111:0.0

Now run ./runInstaller as the oracle user and there will be no issue.