dynamic_shared_memory_type is a a configuration parameter determining which dynamic shared memory implementation to use.
dynamic_shared_memory_type was added in PostgreSQL 9.4.
Possible values are:
Not all values are supported on all platforms.
mmap is not recommended, as the operating system may repeatedly write modified pages back to disk, increasing system I/O load.
The default value for
dynamic_shared_memory_type is the first of the above values supported on the local system.
For Linux et al this will be
posix; for Windows,
mmap is not the default for any platform.