The different reader strategies are described in Reader strategy. Out of the box strategies are:

The default reader strategy is shared. This can be adjusted:

hibernate.search.reader.strategy = not-shared

Adding this property switches to the not-shared strategy.

Or if you have a custom reader strategy:

hibernate.search.reader.strategy = my.corp.myapp.CustomReaderProvider

where my.corp.myapp.CustomReaderProvider is the custom strategy implementation.