HiperSockets multiple write assist with IBM zIIP

When your system is an IBM® System z10® or later server and the HiperSockets multiple write facility is enabled, an additional assist for large outbound TCP messages is available through the IBM Z®® Integrated Information Processor (zIIP) on a System z9® or later server. To enable HiperSockets write processing for large outbound TCP messages on available zIIPs, specify the ZIIP IQDIOMULTIWRITE parameter on the GLOBALCONFIG statement.

When your system is an IBM System z10 or later server that does not have zIIPs configured, you can use the zIIP HiperSockets multiple write facility to project the percentage of existing HiperSockets workload currently running on central processors that would be eligible to run on zIIPs, if zIIPs were available on the z/OS® image. To perform such projection analysis, specify the following parameters on the GLOBALCONFIG statement:

IQDMULTIWRITE parameter
ZIIP parameter with the value IQDIOMULTIWRITE

In addition, you must also specify PROJECTCPU= YES in the IEAOPTxx member of SYS1.PARMLIB. Then run your HiperSockets workload, and SMF provides accounting information regarding zIIP-eligible workload.

Guideline: Remove GLOBALCONFIG ZIIP IQDIOMULTIWRITE from your TCP/IP profile after you have completed your zIIP performance projection runs. TCP/IP consumes slightly more central processing resources when no zIIPs are online and you have coded GLOBALCONFIG ZIIP IQDIOMULTIWRITE.

For information about configuring the PROJECTCPU parameter in the IEAOPTxx member of SYS1.PARMLIB, see z/OS MVS Initialization and Tuning Reference. For information about accounting for zIIP eligibility in SMF record types 30 and 7x, see z/OS MVS System Management Facilities (SMF). For information about zIIP-related reporting updates, see z/OS RMF Report Analysis.