This is the bit that made me think SIGA was a machine instruction: --------------------------Extract from networking on z/OS------------------------------------------------------------- The advantages of using QDIO mode are:
--A 20% improvement in performance versus non-QDIO mode --The reduction of system assist processor (SAP) utilization --Improved response time --Server cycle reduction How is this all accomplished? Instead of attaching an OSA-Express card using a channel, and hence utilizing a channel or I/O program (IOP) combined with CCW operations, the OSA-Express card attaches using an STI bus. STI stands for Self-Timed Interface. The OSA-Express card is still connected within the I/O cage, but the STI bus is directly connected to the memory bus of the CPC. What is used instead of a CCW operation to signify that I/O needs to be completed? With an OSA-Express card running in QDIO mode, I/O operations are effected using a signal adapter instruction, or SIGA. The SIGA is still processed by the SAP, similar to the way a CCW is processed by the SAP. However, the SIGA effectively passes a pointer to the data because the data already occupies internal storage. -----------------------End of extract from networking on z/OS------------------------------------------------------------- >From this I assume that a SSCH instruction is issued for a QDIO sub-channel and this will cause one CCW to be executed with a CCW command code of SIGA. Am I on the right track here ? Thanks. Regards, John. On 4 November 2010 15:27, Vernooij, CP - SPLXM <[email protected]> wrote: > Yes, you are right. > Kees. > > "Bill Fairchild" <[email protected]> wrote in message > news:<77142d37c0c3c34da0d7b1da7d7ca343087ff...@nwt-s-mbx2.rocketsoftware > .com>... >> SSCH is most definitely a machine instruction. >> >> Bill Fairchild >> Rocket Software >> >> -----Original Message----- >> From: IBM Mainframe Discussion List [mailto:[email protected]] On > Behalf Of Vernooij, CP - SPLXM >> Sent: Thursday, November 04, 2010 9:10 AM >> To: [email protected] >> Subject: Re: QDIO question >> >> "John Blythe Reid" <[email protected]> wrote in message >> news:<[email protected]>... >> > I've been looking over the latest ABC of z/OS System programming > book, >> > volume 4, that was published the other day and I read something > about >> > QDIO that made me curious. I notice that QDIO doesn't use channel >> > programs for I/O but uses a SIGA (Signal Adapter) instruction. > Looking >> > at the Principles of Operation there's no SIGA instruction, so where >> > is it ? Does anyone happen to know ? >> > >> > Thanks. >> > >> > Regards, >> > John. >> > >> >> SIGA is not a machine instruction, but a CCW (Channel command), like >> SSCH etx. >> >> > http://publib.boulder.ibm.com/infocenter/zos/v1r9/index.jsp?topic=/com.i >> bm.zos.r9.ieav100/stio.htm >> >> Kees. >> ******************************************************** >> For information, services and offers, please visit our web site: > http://www.klm.com. This e-mail and any attachment may contain > confidential and privileged material intended for the addressee only. 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