create additional oracle 11g database in linux
Oracle Database XE Installation and Execution Restrictions


  Only one installation of Oracle Database XE can be performed on a
  single computer. This does not affect any existing installation or new
  installations of Oracle Database 11g Standard Edition, Oracle Database
  11g Standard Edition One, or Oracle Database 11g Enterprise Edition.
  In addition, users can run only one instance of the Oracle Database XE
  database on each individual computer. To run more than one Oracle
  Database server instance or install more than one copy of the database
  software, upgrade to Oracle Database 11g Standard Edition, Oracle
  Database 11g Standard Edition One, or Oracle Database 11g Enterprise
  Edition.