Splunk DB Connect: If using Output connection to insert in database, how is the Heavy Forwarder supposed to search my events in the index layer?

Dears, i would like to install Splunk DB connect v3 but i have questions regarding recommended setup of it in a Heavy Forwarder. In case i am using Output connection to insert in database, how is the Heavy forwarder supposed to be able to search my events in the index layer? thanks in advance