/RECOVERY_MODE (default)
       /NORECOVERY_MODE

    Enables or disables product installation in recovery mode. The
    directories, files, and libraries that are modified or deleted
    in the installation process are saved in a directory tree on the
    system disk unless you specify /NORECOVERY_MODE. These files,
    along with a copy of the product database, comprise the recovery
    data set.

    The recovery data set is handled somewhat differently when
    an installation ends successfully or if it terminates
    unsuccessfully.

    o  If an installation terminates in its execution phase, either
       voluntarily (by using Ctrl/Y or Ctrl/C) or involuntarily
       (because of a fatal error), the saved recovery data is used to
       roll back all the displaced objects in an attempt to reinstate
       the product environment prior to the interrupted operation.
       Then the recovery data set is deleted.

    o  At the end of the successful installation of one or more full,
       platform, or partial kits, the recovery data set is deleted.

    o  At the end of the successful installation of one or more
       patch or mandatory update kits, the recovery data set is
       automatically retained for possible future use with the
       PRODUCT UNDO PATCH command unless you specify the /NOSAVE_
       RECOVERY_DATA qualifier.