In order for the Solaris SDS to correctly handle and provision Linux RPM's, it needs to be able to extract information from those RPM's. In order to do this it requires the rpm command, which is not a part of standard Solaris.
The rpm command is not a part of the standard Solaris installation.
On the SDS host, install the SFWrpm package from Solaris 10 distribution media or http://www.sun.com/software/solaris/freeware/s10pkgs_download.xml.