Shared Memory (SHM)
Shared Memory (SHM) is our lowest latency communications driver, designed for inter-process communication (IPC). SHM can be used for client and inter-realm (cluster and join) communication. It is operating system independent as it does not depend on any OS specific libraries, making it simple to set up and use.
As the name suggests, shared memory allocates blocks of memory that other processes can access - allowing the same physical computer to make connections without network overhead. This has many advantages, one of which is that when the realm and the data source (publisher) are located on the same physical computer, there is no network latency added between them. This results in less latency for delivery to clients.
No network stack involved
Efficient use of resources with no Network IO required
Same physical machine only
Only currently supported by certain JVMs such as Oracle JDK1.6.0_32, JDK 7, JDK 8 and Azul Zing. On HP-UX systems, shared memory drivers are currently not supported.