Please widen configuration steps for Postgresql database in use with XA transaction under Configuration Guide in section 13.7.2. Vendor-Specific XA Recovery.

Currently the text is

For PostgreSQL to be able to handle XA transaction, change the configuration parameter max_prepared_transactions to a value greater than 0. 

Enhance it with information that `max_prepared_transactions` has to be greater than 0 and should be equal or greater than max_connections.