How to create oracle user for more than one version I have  server under RHEL 6.3 installed on that server Oracle 11gr2 and 12c, I want to create user lets say Ahmad but I want this user to be sysdba on both servers, for single server I edit .bach_profile to be like the following:

11g:

ORACLE_HOSTNAME=oracledev; export ORACLE_HOSTNAME
ORACLE_UNQNAME=DB11G; export ORACLE_UNQNAME
ORACLE_BASE=/oracle11gr2/u01/app/oracle; export ORACLE_BASE
ORACLE_HOME=$ORACLE_BASE/product/11.2.0/db_1; export ORACLE_HOME
ORACLE_SID=DB11G; export ORACLE_SID
PATH=/usr/sbin:$PATH; export PATH
PATH=$ORACLE_HOME/bin:$PATH; export PATH
LD_LIBRARY_PATH=$ORACLE_HOME/lib:/lib:/usr/lib; export LD_LIBRARY_PATH
CLASSPATH=$ORACLE_HOME/jlib:$ORACLE_HOME/rdbms/jlib; export CLASSPATH


PATH=$PATH:$HOME/bin
unset USERNAME
cd $ORACLE_BASE
export PATH


and if I want to make him sysdba for 12c I use the following:

export TMP=/tmp
export TMPDIR=$TMP

export ORACLE_HOSTNAME=oracledev
export ORACLE_UNQNAME=cdb1
export ORACLE_BASE=/oracle12c/u01/app/oracle
export ORACLE_HOME=$ORACLE_BASE/product/12.1.0/db_1
export ORACLE_SID=cdb1

export PATH=/usr/sbin:$PATH
export PATH=$ORACLE_HOME/bin:$PATH

export LD_LIBRARY_PATH=$ORACLE_HOME/lib:/lib:/usr/lib
export CLASSPATH=$ORACLE_HOME/jlib:$ORACLE_HOME/rdbms/jlib


My question is it possible to marge those parameters together without making a conflict, if yes  please advise
For a start you can use oraenv script to set PATH, LD_LIBRARY_PATH, ORACLE_BASE and ORACLE_HOME:

export ORACLE_SID=ORCL

ORAENV_ASK=NO
. /usr/local/bin/oraenv


ORACLE_SID can be parsed from /etc/oratab file. ORACLE_HOSTNAME maybe from HOSTNAME environment variable.