A little research reveals that Oracle (Sun) partner with COMSTAR for the iSCSI connectivity and this page from 2013 says that (at that time) scsi3 PGR was not supported.
How to Configure ISCSI target in Solaris 11 ? - UnixArena
However, there are also a number of comments on the web saying that COMSTAR were about to implement PGR in an update so this is probably available now. Perhaps you might try to download it.