Pointing DB to new Oracle home in primary and standby oracle database
With Grid Infrastructure, you need to modify the configuration with srvctl, for example after upgrading to a new release:

srvctl stop database -d db_unique_name
export ORACLE_HOME=&lt;..new home...&gt;
export PATH=$ORACLE_HOME/bin:$PATH
srvctl upgrade database -d db_unique_name -o oracle_home


Alternatively you can just re-register the database (add back with srvctl from the new home):

srvctl remove database -d db_unique_name
export ORACLE_HOME=&lt;..new home...&gt;
export PATH=$ORACLE_HOME/bin:$PATH
srvctl add database -d dbname -o oracle_home ...


Without Grid Infrastructure, you can start your databases manually, or with a custom script. You need to modify these scripts and update ORACLE_HOME in them. Also, you need to update /etc/oratab if you are on a UNIX/Linux platform. This is also needed if you use the scripts provided by Oracle (dbstart and dbshut).

If you do not have any scripts for starting and stopping the databases, all you need to do is:

shutdown immediate
export ORACLE_HOME=&lt;..new home...&gt;
export PATH=$ORACLE_HOME/bin:$PATH
sqlplus / as sysdba
startup


Finally, do not forget to copy other configuration files from the old home (pfile/spfile, listener.ora, tnsnames.ora, sqlnet.ora, etc.).