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Synchronize time


Synchronize time


How can I synchronize the VMS time with a machine using windows time ?
Is it possible ?
Kris Clippeleyr
Honored Contributor

Re: Synchronize time


Synchronizing which way?
VMS = time source; or Windows = time source.
Both are possible via NTP.

Knowing nothing about Windows...
But for VMS check:


Overhere, we use one of our VMSclusters as time source, and have the NTP server configured, and the Windows machines use NTP client software to synchronize their clocks.

Kris (aka Qkcl)
I'm gonna hit the highway like a battering ram on a silver-black phantom bike...
The Brit
Honored Contributor

Re: Synchronize time

Enable NTP (Network Time Protocol) on both systems. Either have both system synchronize with an external source, or have the windows machine synchronize with the VMS machine.

(recommended, have the VMS machine synch with one of the national time sources, and then have the Windows machine synch with the VMS host.)


Re: Synchronize time

Hi Kris, Hi Dave

Thanks for your informations.
You recommend that I use the VMS to sync the windows system, but I need synch the VMS with the windows machine. I will have problems?
I don't know NTP service, but I will study about. It's easy to configure the NTP service in the VMS system.

best regards
Jan van den Ende
Honored Contributor

Re: Synchronize time


but I need synch the VMS with the windows machine. I will have problems?

Not as long as you define multiple time servers (3 is recommanded anyway), _AND_, you have a guarantee that at least one of those will be running at any time.

(then again, holes in available time server availability are acceptable, as long as they do not last longer as acceptable drift).

So, looks like you are ready to roll!




Have on on me.

Don't rust yours pelled jacker to fine doll missed aches.
Willem Grooters
Honored Contributor

Re: Synchronize time

Syncing the PC against the VMS box has a number of advantages. Most important is that the hardware clock on a VMS box (VAX, Alpha or Itanium) is far superior to any such hardware on a PC. Second, the VMS internal time is updated many times a second, where windows will do once in 2 seconds (if I'm informed correctly). If you miss out a number of updates, VMS tends to drift far less than Windows, even under heavy lodas 9where, in my experience, Windows often looses seconds, if not more. A VMS box won't hang, at least, not as much as a windows box.

If you need to sync against servers on the Internet, I would prefer to use my VMS box for one simple reason: security. I won't trust my Windows-based NTP service to be unhackable/unbreachable.

I use my VMS box to synch against a number of NTP sources on the internet and my PC's against the VMS box. In a number of years, my VMS box has no significant drift and the PC's sync out more than once in a day.
Willem Grooters
OpenVMS Developer & System Manager
Honored Contributor

Re: Synchronize time

Various Windows versions that feature "NTP servers" actually have SNTP servers and not NTP servers, and buggy SNTP servers at that. The newsgroups have various reports of issues with Windows time services with attempts to synchronize from NTP clients from other platforms. (A Google Groups search through comp.os.vms will have various references to SNTP, and SNTP issues.)

OpenVMS and other platforms have NTP clients, and NTP servers. The NTP server can be used by the Windows SNTP client.

You can use either to synchronize against a public NTP server, or you can run OpenVMS or another box with an NTP server and synch against that, or you can also acquire an external time-base (network) box that itself provides an NTP server.

Newer versions of Microsoft Windows may well have NTP servers now. If these issues have been worked out within the Microsoft (S)NTP platform, you may well be able to synchronize to these now.

The OpenVMS FAQ (http://www.hoffmanlabs.com/vmsfaq) has a "chapter" on time and timekeeping and NTP and related.
Jon Pinkley
Honored Contributor

Re: Synchronize time


As others have said, the answer to "Is it possible" is yes. But you haven't answered why you want to do that.

Why is it a requirement for the VMS time to be set to the PC time?

Do you really want someone changing the time on the PC to affect the VMS time?

If you don't want the PC's to set their time based on the VMS system, then use an external NTP server to set both, they will then be reasonably well synchronized.

it depends

Re: Synchronize time

Hi Jon,

Thanks a lot for your considerations. Maybe it is better to think in using the VMS to sync the other Windows Servers. My VMS Servers have access and use more restricted.
I need to consider the possibility to use the VMS with a source time.

Best Regards