Invalid drive passed to disk process.

Occurs on:  86 and 286.  This is an Abend error.

Meaning:  This error indicates that a command to access the disk
          specified a drive that is not on the system.  This is a fatal
          error.  This error is generated by a failed internal
          consistency check and should never occur.

Cause:  This error could be caused by a memory failure in the file
        server and could be attributable to either a hardware failure or
        poor power line conditioning.  A corrupt operating system file
        might also cause this error.

Solution:  Reboot the file server.  If this error or other Abend errors
           occur repeatedly, reinstall the operating system and then
           check the file server's memory and power line conditioning.