ERROR: Target boot environment not identified as being Solaris 10.

I was installing the recommended patch bundle for Solaris 10 and I received an error that the server is not a Solaris 10

root@solaris10:/tmp/patch/10_Recommended # ./installpatchset —-apply-prereq —-s10patchset
ERROR: Target boot environment not identified as being Solaris 10.

root@solaris10:/tmp/patch/10_Recommended # uname -a
SunOS solaris10 5.10 Generic_147440-12 sun4v sparc SUNW,Sun-Blade-T6320

Check two packages SUNWcsr and SUNWcsu

root@solaris10:~ # pkginfo -l SUNWcsr
ERROR: information for “SUNWcsr” was not found

root@solaris10:~ # pkginfo -l SUNWcsu
NAME: Core Solaris, (Usr)
CATEGORY: system
ARCH: sparc
VERSION: 11.10.0,REV=2005.
VENDOR: Oracle Corporation
DESC: core software for a specific instruction-set architecture
PSTAMP: on10-patch20120109151043
INSTDATE: Nov 18 2012 01:12
HOTLINE: Please contact your local service provider
STATUS: completely installed
FILES: 1666 installed pathnames
79 shared pathnames
295 linked files
144 directories
480 executables
30 setuid/setgid executables
30370 blocks used (approx)

In this case, it was missing the file /var/sadm/SUNWcsr/pkginfo

root@solaris10:/var/sadm/pkg/SUNWcsr # ls -l
total 4
drwxr-xr-x 2 root root 512 Nov 18 2012 install
drwxr-x— 27 root root 1024 Nov 18 2012 save

root@solaris10:/var/sadm/pkg/SUNWcsr # ls -l
total 56
drwxr-xr-x 2 root root 1024 Aug 18 2012 install
-rw-r–r– 1 root root 26479 Aug 18 2012 pkginfo
drwxr-x— 49 root root 1024 Aug 18 2012 save

There is two recommendations to solve this problem:
– reinstall the server
– restore from backup

Source: installpatch reports ERROR: Target boot environment not identified as being solaris 10 (Doc ID 1511328.1)