We found that zIIP throughput increased when we turned on SMT-2 threading. But yes, zIIPs always run at full speed, no matter what subcapacity you're running at.
On Mon, Jun 15, 2026 at 9:25 AM Martin Packer <[email protected]> wrote: > One caution on subcapacity and DDF: GCP threads will probably run slower > than zIIP threads. SMT-2 might help reduce this variability - at the > expense of slower threads on zIIP. > > (This is not a recommendation - as it's rather more complex than that - > but an observation.) > > Cheers, Martin > > From: IBM Mainframe Discussion List <[email protected]> on behalf > of John S. Giltner, Jr. <[email protected]> > Date: Monday, 15 June 2026 at 13:09 > To: [email protected] <[email protected]> > Subject: [EXTERNAL] Re: Selecting z model MSU > > How much zIIP workload do you have? You could go to a "smaller" machine > if you have quite a bit of zIIP workload. > > We went from a z14-706 to a z15-608 both having 4 zIIP's. We have a > significant amount of Db2 DDF work. > > So going from "fewer faster" to "more slower" GCP's and having faster > zIIP's our CPU utilization, both GCP and zIIP went down. > > DDF work that was running on GCP's because we did not have enough zIIP > could no go to zIIP's thus reducing work on GCP's. Since the zIIP's were > faster, that work was completing in less time. > > Using zPCR is the way to go as that should help identify what will work > for you and your workload. > > -- > > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, > send email to [email protected] with the message: INFO IBM-MAIN > > Unless otherwise stated above: > > IBM United Kingdom Limited > Registered in England and Wales with number 741598 > Registered office: Building C, IBM Hursley Office, Hursley Park Road, > Winchester, Hampshire SO21 2JN > > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, > send email to [email protected] with the message: INFO IBM-MAIN > -- Jay Maynard ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
