Peter, We are in the process of moving to a z13s. I noticed both the TX the MACHMIG options. We have a tight schedule for the move, do you recommend turning MACHMIG on or off as a start?
Thanks, Kees. > -----Original Message----- > From: IBM Mainframe Discussion List [mailto:[email protected]] On > Behalf Of Peter Relson > Sent: 05 March, 2017 16:50 > To: [email protected] > Subject: Re: Transactional Execution - anybody used it? > > As you might assume, the operating system uses transactional execution. > > A caveat: you cannot use it unconditionally. Even if you know you are on > the right machine. One reason for that is that it cannot be used if z/OS > is running on/under VM. Another is that we have given the customer a > knob > to ask that transactional execution not be used when they are migrating > to > a new machine and really want, first, to make sure that the machine > works > before worrying about whether new code paths in the software also work. > This is the MACHMIG statement of the LOADxx parmlib member. You must pay > attention to the PSA/CVT bit (you can choose which you want to look at) > which is on when available. > > Transactional execution is used, for example, within supervisor, IOS, > RSM. > It is what makes "contractible CPOOL" possible and available. > > We tend to look for cases where we can use TBEGINC rather than TBEGIN. > That is because any use of TBEGIN requires accepting the possibility of > too many aborts, and providing "traditional serialization" in the > fallback > path. And this means that the user of a transaction must also serialize > against the user of "traditional serialization". "Traditional > serialization" could be the local lock, an ENQ, a latch, etc. > > One of the use cases is to avoid coarse-grained serialization when > fine-grained serialization will do. The LOCAL lock is a case of > coarse-grained serialization. It serializes lots of stuff. But sometimes > you might be using it to serialize only "your stuff". Yet you are still > contending for the resource with other users of the LOCAL lock, so could > be adversely impacted by those cases (and your usage could adversely > impact others). If you can use TBEGIN(C), you no longer need to contend > with other users of the LOCAL lock. > > This is a performance-related facility. Performance needs should dictate > how much you choose to use it. > > Peter Relson > z/OS Core Technology Design > > > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, > send email to [email protected] with the message: INFO IBM-MAIN ******************************************************** 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. If you are not the addressee, you are notified that no part of the e-mail or any attachment may be disclosed, copied or distributed, and that any other action related to this e-mail or attachment is strictly prohibited, and may be unlawful. If you have received this e-mail by error, please notify the sender immediately by return e-mail, and delete this message. Koninklijke Luchtvaart Maatschappij NV (KLM), its subsidiaries and/or its employees shall not be liable for the incorrect or incomplete transmission of this e-mail or any attachments, nor responsible for any delay in receipt. Koninklijke Luchtvaart Maatschappij N.V. (also known as KLM Royal Dutch Airlines) is registered in Amstelveen, The Netherlands, with registered number 33014286 ******************************************************** ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
