SPECIAL INSTRUCTIONS FOR DIGITAL UNIX 4.0E PATCH 591.00 
NOTE: In order to activate I/O throttling/smooth sync, you must install
      Patch 568.00.  These patches do not have dependencies on each other;
      this means the dupatch utility will not warn you if you do not select
      all of these patches.

NOTE: Smooth Sync is for UFS only.

Update your /etc/fstab entries to enable the selected mount options
on the selected UFS filesystems. These mount options are described in
the the release note for I/O Throttling / Smooth Sync. See the Patch
Summary and Release Notes for further information.

If you are going to remove this patch, see the Patch Summary and Release
Notes for further information; not doing so may result in an unusable
system.