If you use Solaris Volume Manager software, you must set aside a slice on the root disk for use in creating the state database replica. Specifically, set aside a slice for this purpose on each local disk. But, if you have only one local disk on a Solaris host, you might need to create three state database replicas in the same slice for Solaris Volume Manager software to function properly. See your Solaris Volume Manager documentation for more information.
If you use Veritas Volume Manager (VxVM) and you intend to encapsulate the root disk, you need to have two unused slices that are available for use by VxVM. Additionally, you need to have some additional unassigned free space at either the beginning or the end of the disk. See your VxVM documentation for more information about root disk encapsulation.