To create a new branch, in Eclipse in the svn repository explorer, right click on the folder 12.11-RC and select create branch. The new location should be something like http://halsvn01/svn/hal/branches/features/fix-security-settings
Or from the command line:
$ svn copy http://halsvn01/svn/hal/branches/RC/12.11-RC http://halsvn01/svn/hal/branches/features/simplified-welcome-page -m "Creating feature branch simplified-welcome-page"