CSM provides a means for authorized host applications to share data with other CSM users without having to copy the data. (A CSM user can be any system-authorized application program or product.) CSM is also used by VTAM® on behalf of any VTAM LU 6.2 application, authorized or not, to transfer data between CSM buffers and the multipath channel with fewer data moves. Applications can create buffer pools in CSM and load data in buffers, which are represented by buffer tokens. Ownership of these buffers can be changed to allow other CSM users to assume responsibility for storage return to CSM. This allows an application and VTAM to exchange ownership of a single piece of commonly addressable storage so that there is no need to move the data at the APPCCMD API. VTAM uses the same CSM storage area for channel I/O. CSM storage is either data space or extended common service area (ECSA) storage.

CSM provides an API (IVTCSM) that enables applications to request CSM services, such as registering to use a pool of buffers, getting or freeing a number of buffers from a pool, or changing the ownership of a buffer. For more information about the CSM requests available to the application, refer to z/OS Communications Server: CSM Guide.

For more complete information about CSM, refer to z/OS Communications Server: CSM Guide.