Bob, including Linux in a GDPS/XRC environment is generally fine, also without ETR or STP support for time synchronization.
As far as I can see you only have the need for a data consistency group throughout multiple Linux images or between Linux and z/OS if you have transactional data in your multi-tier setup that requires time consistency in case of an outage for proper rollback processing. Remember your respective logs get (implicitly) synchronized through the z/OS data mover based on the time stamps. With the logs in case of an outage getting out of sync due to time inconsistency (one side thinks the 2-phase commit completed successfully and the other side perhaps not even finding the transaction it in its logs at all) the recovery process is getting more "complicated" ... However, please be aware that this becomes an issue *only* if the LPAR hypervisor can't adjust the time transparently (which it usually does) and therefore depends on OS collaboration. You may call this paranoia, but it is real. Without OS support for respective machine checks the hypervisor is required to virtualize the TOD for the OS not participating and thus the respective OS images start working on different TOD values. Therewith what used to be a consistency group will show a time shift between images. Hence all OS images that have the requirement for a consistency group (as outlined above) better collaborate on ETR/STP time synchronization. We are working to provide ETR support asap, but currently this anticipated support is limited to LPAR only, as z/VM doesn't provide the required guest support, yet. STP will follow. Best regards, Ingo -- Ingo Adlung, STSM, System z Linux and Virtualization Architecture mail: [EMAIL PROTECTED] - phone: +49-7031-16-4263 Linux on 390 Port <LINUX-390@VM.MARIST.EDU> wrote on 11.10.2006 18:11:51: > Ingo, > > I am a GDPS/XRC environment and I *will* want Linux to participate > there. What is the answer or issues I face? > > Bob Richards > > > > -----Original Message----- > From: Linux on 390 Port [mailto:[EMAIL PROTECTED] On Behalf Of > Ingo Adlung > Sent: Wednesday, October 11, 2006 12:05 PM > To: LINUX-390@VM.MARIST.EDU > Subject: Re: Server Time Protocol support for zSeries > > The only use case I'm aware of where standard NTP usage is not > accurate enough, but asking for ETR or STP usage is when you want > Linux to participate in an XRC asynchronous replication scheme *and* > you have a requirement for building XRC time consistency groups > across multiple OS images. Those might either be homogeneous Linux > or heterogenous Linux and z/OS environments where the z/OS data > mover replicates data based on TOD timestamps and you can't tolerate > time inconsistency in case of an outage. > > Best regards, > Ingo > > -- > Ingo Adlung, > STSM, System z Linux and Virtualization Architecture > mail: [EMAIL PROTECTED] - phone: +49-7031-16-4263 > > Linux on 390 Port <LINUX-390@VM.MARIST.EDU> wrote on 11.10.2006 > 17:40:42: > > > > -----Original Message----- > > > From: Linux on 390 Port [mailto:[EMAIL PROTECTED] On > > > Behalf Of Dave Jones > > > Sent: Wednesday, October 11, 2006 10:31 AM > > > To: LINUX-390@VM.MARIST.EDU > > > Subject: Re: Server Time Protocol support for zSeries > > > > > > > > > That's a good question, John. As far as I know, Linux on > > > zSeries (either > > > VM guest or native) can use an external time source to set its > clock. > > > > > > The real problem is that z/VM and it's guests can not use the > > > same time > > > source as z/OS to sync their clocks together. Consider the case > where > > > there are two LPARS in a z9-BC, one running z/OS and using STP to > set > > > its clock and the other LPAR running z/VM and Linux guests > > > with its time > > > set by the operator's Timex. :-) > > > > > > DJ > > > > I'm still a bit confused. I know that z/VM cannot set its clock to the > > STP time source. But why couldn't the Linux systems under z/VM use > XNTP > > to set their clock to the z/OS value? z/OS 1.7 can run an NTP daemon > > which the Linux instances should be able to use. I hope that would be > > "close enough". > > > > -- > > John McKown > > Senior Systems Programmer > > HealthMarkets > > Keeping the Promise of Affordable Coverage > > Administrative Services Group > > Information Technology > > > > This message (including any attachments) contains confidential > > information intended for a specific individual and purpose, and its > > content is protected by law. 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