Setup your environment variables

-- Add the below in your .bash_profile
#Oracle Profile
export ORACLE_BASE=/u01/app/oracle
export ORACLE_HOME=$ORACLE_BASE/product/12.1.0./dbhome_1
export ORACLE_SID=orcl
export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:$ORACLE_HOME/lib
export PATH=$ORACLE_HOME/bin:$ORACLE_HOME/perl/bin:$PATH

alias sql='sqlplus / as sysdba'
alias orcl="export ORACLE_SID=orcl; sqlplus / as sysdba"
alias dwhdb="export ORACLE_SID=dwhdb; sqlplus / as sysdba"
alias net="cd $ORACLE_HOME/network/admin"
alias dbs="cd $ORACLE_HOME/dbs"

-- Reload the oracle bash profile
[oracle@srv1 ~]$ . !$
 . ~/.bash_profile
 [oracle@srv1 ~]$ . ~/.bash_profile
 [oracle@srv1 ~]$