parallel_instances 

This parameter is only relevant if you are using Oracle Real Application Cluster (RAC).

The instances running in parallel to the dedicated database instance are defined by this parameter.

Syntax:

parallel_instances = <inst_descr>|(<inst_descr_list>)

Default: none.

<inst_descr>: <ORACLE_SID>:<ORACLE_HOME>@<conn_name>

<ORACLE_SID>: Oracle System ID of the parallel instance

<ORACLE_HOME>: ORACLE_HOMEdirectory of the parallel instance

<conn_name>: Oracle connection name from TNSNAMES.ORA for connect to the parallel instance

parallel_instances = (RAC001:/oracle/RAC/101_64@RAC001,
RAC002:/oracle/RAC/102_64@RAC002,
RAC003:/oracle/RAC/101_64@RAC003

Specify all database instances in this parameter.