A read-only SQL transaction cannot alter non-temporary tables. This parameter controls the default read-only status of each new transaction. The default is
Consult sql-set-transaction for more information.
This setting is mainly useful for preventing yourself from accidentally changing data. It is not really a security setting, as anyone can revoke it on their own session. Better set on a session or ROLE level. Will show up as TRUE if you are on a replication standby.