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In the third and final part of our series examining how SyncSort for z/OS exploits the advanced facilities of the z/OS operating system and zSeries computers, we take a look at zIIP technology. Click through to catch up on the previous articles where we covered MIDAW and PAV technology.

What is zIIP?

 The System z9 Integrated Information Processor (zIIP) is a specialty engine that is available on System z9 mainframes. It is intended to lower the overall cost of mainframe ownership. The machine cycles on these processors do not factor into the MSU calculation for the capacity of a mainframe. This can reduce system-wide software costs.

The Workload Manager (WLM) component of z/OS is responsible for directing work to the general purpose processors and the zIIP engines. The unique nature of the zIIP places restrictions on the type of work that this processor can handle.

Only a preemptible enclave Service Request Block (SRB) will be dispatched on a zIIP. This is a very specific and restrictive type of workload, but for software products that can conform to these limitations, the zIIP offers a way to lower CPU time costs.

Figure 1: Configuration differences possible with zIIP

To demonstrate the power of the zIIP, suppose the workload of a particular company required a mainframe capable of 640 MSUs. This is represented by the configuration above on the left. If the work on that particular mainframe was such that it could be accomplished with only 8 general purpose processors and 2 zIIPs, the company would be able to license the configuration above on the right. The difference in MSU capacity between these 2 configurations is 108 or 16.9%. Since all software pricing on this machine is based on the reduced number of MSUs, savings can be realized on software products on this machine even if they are not able to exploit the zIIP.

DB2 was the initial IBM subsystem that exploited the zIIP. This exploitation significantly improves the performance of DB2 while lowering software costs across the board. It has proven to be very popular.

How Does SyncSort for z/OS Exploit zIIP?

There are many processes that occur during a sort. During the input phase, the input files need to be read, records need to be de-blocked and manipulated, data utility functions need to be performed, the sorting process must begin and records need to be moved to SORTWK files. Similar processing occurs during the output phase. SyncSort achieves performance benefits by the seamless integration and overlap of these different processes. Some of these processes are CPU-intensive, some are I/O-intensive, and some are dependent on system services through SVC calls. The I/O and SVC processes are not eligible for zIIP processing.

In order to exploit the zIIP technology, SyncSort developers isolated and restructured some of SyncSort’s more intensive CPU processes. By reorganizing code to separate functions that could be managed independently, the developers were able to create stand-alone units of work and repackage them as SRBs. These zIIP-eligible SRBs can be passed to WLM in a way that will allow them to be dispatched to a zIIP. All of this work is accomplished without the awareness or involvement of the user. SyncSort’s use of the zIIP is available in Release 1.3.

Offloading these sort processes to a zIIP lowers the traditional CPU time cost associated with sorting. This decreases the MSU demand on the mainframe which can lead to substantial software savings.

Conclusion

Syncsort is committed to providing the best performance possible as computers and operating systems continue to evolve. The exploitation of PAV, MIDAW and zIIP demonstrates the high level of technical sophistication built into SyncSort for z/OS.

Significantly, the performance improvements are automatic. SyncSort determines if a given application can benefit from using these features without requiring any modification to individual jobs.

If you would like further information related to SyncSort performance, please contact us or call us at (02) 9956 8555.

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