Log in as the oracle user:
su - oracle
Edit .bash_profile in oracle's home directory and add the following, for instance using vim:
########## Oracle Variables ########## echo " Welcome to oracle"; ORACLE_BASE=/u01/app/oracle ORACLE_OWNER=oracle; export ORACLE_OWNER ORACLE_TERM=xterm; export ORACLE_TERM ORACLE_HOME=/u01/app/oracle/product/9.2.0.1.0 ORACLE_SID=ORTD LD_PRELOAD=$HOME/libcwait.so export DISPLAY=172.28.66.39:0.0 PATH=$PATH:$ORACLE_HOME/bin LD_LIBRARY_PATH=$LD_LIBRARY_PATH:$ORACLE_HOME/lib:$ORACLE_HOME/network/lib CLASSPATH=$ORACLE_HOME/JRE:$ORACLE_HOME/jlib:$ORACLE_HOME/rdbms/jlib export CLASSPATH LD_ASSUME_KERNEL=2.4.1; export LD_ASSUME_KERNEL THREADS_FLAG=native; export THREADS_FLAG TMP=/tmp; export TMP TMPDIR=$TMP; export TMPDIR export PATH ORACLE_BASE ORACLE_HOME ORACLE_SID LD_LIBRARY_PATH LD_PRELOAD ########## End of Oracle variables ##########