TCP autonomic tuning enhancements

z/OS® Communications Server makes the following enhancements to automatically tune resources that are related to TCP connections. The enhancements are based on real-time data and can improve overall performance of TCP connections.

Dynamic Right-Sizing (DRS) and Outbound Right-Sizing (ORS) autonomics
DRS and ORS are z/OS Communications Server optimizations that improve overall performance for certain high latency streaming workloads. z/OS Communications Server V2R2 lifts restrictions on which workloads and applications are eligible for each optimization and makes each optimization more sensitive to connection and CSM ECSA storage conditions. In addition, TCP/IP can stop and restart the DRS optimization dynamically for each connection based on the current system or application responsiveness.
Delayed transmission of acknowledgment autonomics
z/OS Communications Server delays the transmission of acknowledgments on a TCP connection based on user configuration settings. z/OS Communications Server V2R2 provides autonomic capability to monitor the effectiveness of delaying the transmission of acknowledgments on a connection and a listener level. In addition, TCP/IP can stop and restart the delaying transmission of acknowledgments for each connection based on workload and application characteristics.
Fast Retransmit, Fast Recovery (FRR) autonomics
z/OS Communications Server V2R2 extends the detection of out-of-order packets to lost packets during FRR recovery. When FRR recovery processing completes and no lost packets are detected , TCP/IP restores the transmission rates that were allowed before FRR recovery processing.

Enhancing TCP autonomic tuning

To automatically tune resources that are related to TCP connections, complete the tasks in Table 1.

Table 1. Enhance TCP autonomic tuning
Task/Procedure	Reference
Take the following steps to enable TCP/IP to autonomically determine when to delay transmission of acknowledgments: Code the TCPCONFIG AUTODELAYACKS statement. Optionally, if you previously coded NODELAYACKS on PORT, BEGINROUTES, OMPROUTE statements or POLICY definitions, remove the NODELAYACKS definitions so that TCP/IP can determine the appropriate setting.	TCPCONFIG statement in z/OS Communications Server: IP Configuration Reference
Issue the Netstat ALL/-A command to determine the following information about a specific TCP connection: Whether the connection is eligible for delayed transmission of acknowledgments, and if the connection is eligible, whether acknowledgments are delayed. Whether the connection is eligible for DRS optimization, and if the connection is eligible, whether the DRS optimization is performed. Whether the connection is eligible for ORS optimization, and if the connection is eligible, whether the ORS optimization is performed. Whether new TCP connections to the listener application are started by using delayed transmission of acknowledgments.	Netstat ALL/-A report in z/OS Communications Server: IP System Administrator's Commands
Issue the Netstat CONFIG/-f command to identify whether the stack can automatically control the delayed transmission of acknowledgments for TCP connections.	Netstat CONFIG/-f report in z/OS Communications Server: IP System Administrator's Commands