After OS upgrade ...

The only important thing after the OS upgrade on a host with Oracle db is to relink binaries.

## before it is good to find all the files owned by root
## after the relink operation they would become again owned by oracle
[oracle@host1 ~]$ find $ORACLE_HOME -user root -exec ls -l {} \;
-rw-r-----   1 root     oinstall    1534 Dec 21  2005 /oracle/product/11.2.0.3/rdbms/admin/externaljob.ora
-rwsr-x---   1 root     oinstall 1340408 Sep 25  2011 /oracle/product/11.2.0.3/bin/oradism
-rws--x---   1 root     oinstall   29216 Jun 21  2013 /oracle/product/11.2.0.3/bin/nmo
-rws--x---   1 root     oinstall   21624 Jun 21  2013 /oracle/product/11.2.0.3/bin/nmb
-rwsr-x---   1 root     oinstall 1277904 Jun 21  2013 /oracle/product/11.2.0.3/bin/extjob
-rws--x---   1 root     oinstall   93296 Jun 21  2013 /oracle/product/11.2.0.3/bin/nmhs
-rwsr-x---   1 root     oinstall   26824 Jun 21  2013 /oracle/product/11.2.0.3/bin/jssu


[oracle@host1 ~]$ cd $ORACLE_HOME
[oracle@host1 ~]$ ./bin/relink all

## after the relink operation some of binaries, which have to be owned by root are 
## again owned by oracle; after the installation the permissions are set by root.sh
## now it is enough to run the commands below, as root.sh does more things

[oracle@host1 ~]$ chown root $ORACLE_HOME/rdbms/admin/externaljob.ora
[oracle@host1 ~]$ chmod 640 $ORACLE_HOME/rdbms/admin/externaljob.ora
[oracle@host1 ~]$ chown root $ORACLE_HOME/bin/oradism
[oracle@host1 ~]$ chmod 4750 $ORACLE_HOME/bin/oradism
[oracle@host1 ~]$ chown root $ORACLE_HOME/bin/nmo
[oracle@host1 ~]$ chmod 4710 $ORACLE_HOME/bin/nmo 
[oracle@host1 ~]$ chown root $ORACLE_HOME/bin/nmb
[oracle@host1 ~]$ chmod 4710 $ORACLE_HOME/bin/nmb
[oracle@host1 ~]$ chown root $ORACLE_HOME/bin/extjob
[oracle@host1 ~]$ chmod 4750 $ORACLE_HOME/bin/extjob
[oracle@host1 ~]$ chown root $ORACLE_HOME/bin/nmhs
[oracle@host1 ~]$ chmod 4710 $ORACLE_HOME/bin/nmhs
[oracle@host1 ~]$ chown root $ORACLE_HOME/bin/jssu
[oracle@host1 ~]$ chmod 4750 $ORACLE_HOME/bin/jssu