Planning your z/OS® TCP/IP environment

To get the best throughput through your network, you must use TCP/IP send and receive buffers with a size of 64 KB, or greater. With this size, the system optimizes its buffer sizes.

See Dynamic right sizing for high latency networks for more information.

You can check your system buffer size by using the following Netstat command, for example:


TSO NETSTAT ALL (CLIENT csq1CHIN

The results display much information, including the following two values:


ReceiveBufferSize: 0000065536
SendBufferSize: 0000065536

65536 is 64 KB. If your buffer sizes are less than 65536, you must work with your network team to increase the TCPSENDBFRSIZE and TCPRCVBUFRSIZE values in the PROFILE DDName in the TCPIP procedure. For example, you might use the following command:


TCPCONFIG TCPSENDBFRSZE 65536 TCPRCVBUFRSIZE 65536

If you are unable to change your system-wide TCPSENDBFRSIZE or TCPRCVBUFRSIZE settings, contact your IBM® Software Support center.