How to find out if a parameter in PostgreSQL is dynamic or not

Oracle has both dynamic and static parameters, meaning that the former can be set in a session and while the database is up, while the latter cannot.

To find out if a parameter in PosgreSQL is dynamic, you can use the query

select context from pg_settings where name = 'enable_parallel_hash';

Result:

 context
---------
 user
(1 row)

"user" means that the parameter can be set in a user's session. Thanks to Daniel Westerman for writing the useful article where I found this useful information.