Se voce tiver os discos de instalacao pode copiar eles em uma pasta por exemplo /stage/
E deve adicionar essas informacoes criando um arquivo  media.repo na pasta /etc/yum.repos.d assim o yum ira funcionar normalmente.

[root@srvoracle01 yum.repos.d]# pwd
[root@srvoracle01 yum.repos.d]# cat media.repo
name=Red Hat Enterprise Linux $releasever

Ou seguir os passos abaixo para fazer a configuracao do repositorio do YUM.

Getting Started

   1. Download and Install Enterprise Linux

      Download and copy the appropriate yum configuration file in place, by running the

following commands as root:
      Oracle Enterprise Linux 4, Update 6 or Newer

      # cd /etc/yum.repos.d
      # mv Oracle-Base.repo Oracle-Base.repo.disabled
      # wget

      Oracle Enterprise Linux 5

      # cd /etc/yum.repos.d
      # wget

      Oracle VM 2

      # cd /etc/yum.repos.d
      # wget


      Enable the appropriate repository by editing the yum configuration file
          * Open the yum configuration file in a text editor
          * Locate the section in the file for the repository you plan to update from,

e.g. [el4_u6_base]
          * Change enabled=0 to enabled=1

      Begin using yum, for example:

      yum list

      yum install firefox

You may be prompted to confirm the import of the Oracle OSS Group GPG key.