Joined: 06 Jun 2008 Posts: 8165 Location: East Dubuque, Illinois, USA
Assuming the OMVS root file system is HFS, if it goes into secondary extents it'll automatically use them. Not really a problem.
Depending on the z/OS version you may be required to IPL to implement the new root HFS file system. I'd probably use DFDSSDFP to dump the old root into a backup file, then restore into the new file system.