This is marked PGC_SIGHUP, so it can only be set in a configuration file, not anywhere else; and it is also marked GUC_DISALLOW_IN_AUTO_FILE, so it can't be set using ALTER SYSTEM. When set to false, the ALTER SYSTEM command is disallowed. There was considerable concern that this would be misinterpreted as a security feature, which it is not, because a determined superuser has various ways of bypassing it. Hence, a lot of work has gone into wordsmithing the documentation, in the hopes of avoiding any such confusion. Jelte Fennemia-Nio and Gabriele Bartolini, with wording suggestions for the documentation from many others. Discussion: http://postgr.es/m/CA%2BVUV5rEKt2%2BCdC_KUaPoihMu%2Bi5ChT4WVNTr4CD5-xXZUfuQw%40mail.gmail.com
PostgreSQL Database Management System
This directory contains the source code distribution of the PostgreSQL database management system.
PostgreSQL is an advanced object-relational database management system that supports an extended subset of the SQL standard, including transactions, foreign keys, subqueries, triggers, user-defined types and functions. This distribution also contains C language bindings.
Copyright and license information can be found in the file COPYRIGHT.
General documentation about this version of PostgreSQL can be found at https://www.postgresql.org/docs/devel/. In particular, information about building PostgreSQL from the source code can be found at https://www.postgresql.org/docs/devel/installation.html.
The latest version of this software, and related software, may be obtained at https://www.postgresql.org/download/. For more information look at our web site located at https://www.postgresql.org/.