The shared memory cushion is part of the shared memory area. Its function is to handle short-term high demands on the server. When an enterprise server instance starts, the shared memory cushion is not available for use, and it is never used by incoming client requests. It is used only when a response needs to be passed back to a client, and there is insufficient free memory in the main area to handle the response.
The shared memory cushion is also measured in pages of 4KB each. Set the shared memory cushion to 10% of the size of the shared memory area.