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Zone Offset and TOD under z/VM in a DR situation

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Stuart, David

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Sep 21, 2016, 3:51:31 PM9/21/16
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Afternoon all,

 

We ran a DR test last Friday, and a minor, nuisance-level issue that’s been going on for years is related to the Time Zone offsets and TOD.

 

In a DR situation, we run as a guest System under z/VM. The hardware is set to UTC, and z/VM have the correct zone offset and ‘local’ time for where it is located. When my z/VSE System came up, the time was incorrect. It was an hour behind my ‘local’ time, which is Pacific Daylight Time, which is that I think it should have been. Instead, the System time was as if it was running Pacific Standard time.

 

My IPL proc for DR has all the same Set Zonedef and Set Zonebdy statements as my Production IPL Proc (we don’t have z/VM at ‘home’). The Systems here all run with the correct Zone offset and time. My z9 hardware TOD clock is set to UTC.

 

I spoke with the z/VM System Programmer for our DR Provider. He was suggesting that I need to issue Query VTOD and SET VTOD commands to set the time correctly, so that my z/VSE 5.2 System will come up with the correct time and zone offsets.

 

I know that a number of you run under z/VM, both at ‘home’ and/or in a DR situation. What do you do, under z/VM in a DR situation, so that the recovered z/VSE System comes up with the correct zone offset and time, even though the z/VM System you’re running on is not in the time zone where the z/VSE System ‘belongs’?

 

 

Thanks,

Dave

 

 

Dave Stuart

Principal Information Systems Support Analyst

Information Technology Services

County of Ventura, CA

805-662-6731

David....@ventura.org

 

Kris Buelens

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Sep 21, 2016, 5:12:42 PM9/21/16
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Unless you use 'SET TIMEZONE VM' (or something that looks like that, I don't know the exact syntax), z/VSE doesn't use VM's timezone at all.  It gets the time from the HW.

If you issue SET VTOD in the VM guest, VM will store an offset in the SIE control block (that describes the virtual machine), and the time obtained by Store Clock is adjusted accordingly.  Similar: if you enter a date&time during the VSE IPL, an offset is calculated and stored in the SIE control block.

So, I'd guess the HW at the DR centre is not set to UTC... (or your 'home' z9 isn't set to UTC)


Kris Buelens,
     --- freelance z/VM consultant, Belgium ---
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Dennis McLoud

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Sep 21, 2016, 9:04:58 PM9/21/16
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Use your TCP/IP to set the time during IPL.  Does not matter what the hardware is set to.  Using NTP to set your system clock will make your IPL hardware independent. Of course this assumes connectivity. The set time batch job can be run any time after you have TCP/IP working. Just make sure not to have anything time sensitive running until this step is complete.

 

Dennis McLoud

Systronics

913-956-6261

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