Permission for root to access oracle

I installed oracle10g on Redhat Enterprice Linux.

For that, I created Oracle user and installed oracle on oracle user.
root or any other users do not have permission to access oracle.
I want to set permission for the root as well as for other users to access oracle.

How will I do that?

Oracle permissions are not the same as OS permissions. The Oracle database user permissions are managed by Oracle itself, so you need to consult the Oracle docs.

Because the Oracle server is an OS process, it's assigned to an OS user in order to keep the OS secure, but the database users talk to the server, not to the OS.

I recently installed Oracle 10g Express Edition (the free version of Oracle) on an Ubuntu machine. To be able to start and stop the database and do other things, I had to make myself a member of the 'dba' group. Read the Oracle documentation.

That's right. Since Oracle itself is an OS process, if you want to control the Oracle server, you need appropriate OS privileges. If you just want to work inside of Oracle, you need an Oracle user acount. You can have either one or both, depending on how you need to interact with Oracle.