If a file system is damaged, you can recover by replacing it with a saved version that was created from an earlier backup. To recover a backed up file system, you must perform the following tasks:

1. Notify all users to stop all activity on the damaged file system.
2. Have an authorized user enter the TSO/E UNMOUNT command with the IMMEDIATE option to logically unmount the damaged file system. If the unmount fails, reenter the UNMOUNT command with the FORCE option.
3. Use the DFSMSdss dump utility to restore the backed up file system to a replacement file system (HFS data set). You can do this simultaneously with the previous steps.
4. Have an authorized user enter a TSO/E MOUNT command to logically mount the replacement file system. Ensure that the MOUNT commands in the BPXPRMxx member in SYS1.PARMLIB are consistent with this MOUNT command.
5. Issue a broadcast message to all users or a message to all z/OS® UNIX users when they invoke the shell, telling them that you have mounted a back-level file system and informing them of the mount point. Users must recreate and add any files added since the file system was backed up.

You might choose a more disruptive method to recover a backed up file system for the root file system. Refer to z/OS UNIX System Services Planning, “Shutting Down z/OS Unix“, for more information on how to perform a shutdown.