D.3.2 Internal Shared Memory technology overview ISM is a function that is supported by the z14, z13, and z13s systems. It is the firmware that  provides the connectivity for shared memory access between multiple operating systems  within the same CPC. It provides the same functionality as SMC-R, but without physical  adapters (such as the RoCE adapter) by using instead virtual ISM devices as SMC-R. It is a  HiperSocket-like function that provides guest-to-guest communications within the same  machine. A possible solution that uses only SMC-D is shown in Figure D-10. SMC-D and SMC-R technologies can be used at the same time on the same CPCs. A fully  configured three-tier solution that uses SMC-D and SMC-R is shown in Figure D-11.  z/OS z/OS LP 1 LP 2 DB2 ISM VCHID DRDA  System z vPCI Firmware Shared Memory Communications vPCI ISM Virtual Function vPCI ISM Virtual Function Sockets  SMC SMC  Sockets CICS Shared Mem Shared Mem FID 1 FID 2 SMC-R and SMC-D enabled platform z/OS image 1 (WAS) z/OS image 3 (WAS) Shared Memory Communications  via DMA (SMC-D using vPCI ISM) client Shared Memory Communications via RDMA (SMC-R using RoCE) SMC RDMA enabled (RoCE) Clustered Systems: Example: Local and Remote access to DB2 from WAS (JDBC using DRDA) SMC-R enabled platform shared memory Sockets SMC Server shared memory Sockets z/OS image 2 (DB2) shared memory client Sockets SMC RoCE RoCE ISM ISM VCHID Figure D-10 Connecting two LPARs on the same CPC by using SMC-D Figure D-11 Clustered systems: Multitier application solution. RDMA, and DMA D.3.3 SMC-D over Internal Shared Memory ISM is a virtual channel that is similar to IQD for HiperSockets. A virtual adapter is created in  each OS. The memory is logically shared by using the SMC protocol. The network is  firmware-provided and a new device is required to manage that virtual function. SMC is based  on a TCP/IP connection and preserves the entire network infrastructure. SMC-D is a protocol that allows TCP socket applications to transparently use ISM. It is a  “hybrid” solution, as shown in Figure D-12 on page 440. Appendix D. Shared Memory Communications  439