[Oracle Active DataGuard 12.1 Installation on Centos 6.7]: Starting instance on standby

$ cd $ORACLE_HOME/dbs

Creating a pfile with a single parameter - the database name

$ echo DB_NAME=${ORACLE_SID} > init${ORACLE_SID}.ora

$ sqlplus / as sysdba

SQL> startup nomount pfile=$ORACLE_HOME/dbs/init${ORACLE_SID}.ora

SQL> select status from v$instance;

STATUS
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STARTED