One problem description
SQL> startup
ORA-01078: failure in processing system parameters
ORA-01565: error in identifying file '+SYSTEM/itpux/spfileitpux.ora'
ORA-17503: ksfdopn:2 Failed to open file +SYSTEM/itpux/spfileitpux.ora
ORA-12547: TNS:lost contact
SQL> exit
Two solutions
su - grid
chmod 6751 $GRID_HOME/bin/oracle
ls -l oracle
-rwsr-s--x 1 grid oinstall 152400480 Nov 24 15:49 oracle
su - oracle
chmod 6751 $ORACLE_HOME/bin/oracle