ORA-01078: failure in processing system parameters LRM-00109: could not open parameter file

Sometimes while trying to start oracle database the following errors may happen

ORA-01078: failure in processing system parameters
LRM-00109: could not open parameter file

This could be due to the invalid value for the ORACLE_SID environment value

To verify the valid value for SID execute the following command

cat /etc/oratab


[oracle@fmw12c ~]$ cat /etc/oratab
#

# This file is used by ORACLE utilities.  It is created by root.sh
# and updated by either Database Configuration Assistant while creating
# a database or ASM Configuration Assistant while creating ASM instance.

# A colon, ':', is used as the field terminator.  A new line terminates
# the entry.  Lines beginning with a pound sign, '#', are comments.
#
# Entries are of the form:
#   $ORACLE_SID:$ORACLE_HOME:<N|Y>:
#
# The first and second fields are the system identifier and home
# directory of the database respectively.  The third field indicates
# to the dbstart utility that the database should , "Y", or should not,
# "N", be brought up at system boot time.
#
# Multiple entries with the same $ORACLE_SID are not allowed.
#
#
fmw12c:/opt/app/oracle/db/product/12.1.0/dbhome_1:N

---------------------------------------------------------------

At the end of the file the valid SIDs will be visible as shown above.

Now set the ORACLE_SID to any of the valid value from the above file

\[oracle@fmw12c ~]$ export ORACLE_SID=fmw12c

After this logon to sqlplus as sysdba

Then execute startup

SQL> startup