On a system with non-global zones, it is recommended not to use the patchadd -M option. The current implementation of patchadd -M applies all the patches to the global zone first, and only then to the non-global zones. This is sub-optimal, because if an issue occurs after a number of patches have been applied to the global zone but not to the non-global zone, the zones may be significantly out of sync with each other, making the situation potentially difficult to recover.
Workaround: patchadd -a -M can be used to construct a valid install sequence for a set of patches and to ensure that the patches should install without an issue.
For more information, see the Best Practices article on the BigAdmin Patching Hub, at http://www.sun.com/bigadmin/features/articles/patch_management.jsp.