The message portion contains the message buffers that the shared-memory communication interface uses. The amount of space required for these buffers depends on the number of user connections that you allow using a given networking interface. If a particular interface is not used, you do not need to include space for it when you allocate shared memory in the operating system. You can use the following formula to estimate the size of the message portion in kilobytes:
msegsize = (10,531 * ipcshm_conn + 50,000)/1024