Is it possible/advisable to use time synchronization under i5 ?

[Former Member]

I have read that it is possible to configure one or more partitions in a iSeries machine to use time the synchronization protocol (SNTP).

Is it advisable, from the SAP perspective, to use that synchronization ?

I have heard from some people that SAP could have problems when the system clock is adjusted while SAP is running. Is it true ?

If the answer is that it is not advisable, can anyone suggest another way to synchronize the time between partitions with our central company clock ?

We are running iSeries ver 5R3, and SAP is running with WAS 6.40.

Thanks, Victor.

[Former Member]

We too take extreme care in this area - not something to meddle with. We always stop SAP and in the case of the time going back wait an hour to ensure that there are no possible time conflicts with transactions.

[Former Member]

Hello everyone,

I guess nobody has configured out a way to avoid the one-hour downtime when the clock moves backwards...

Anyone tried using SNTP to adjust that one hour? Or want to try it like below? Using EST time as example

1. Shut down SAP before 1:59 AM EDT

2. one minute later, system should adjust QTIME back to 1:00 AM EST

3. one minute later, Manually set QTIME to 2:01AM EST

4. Start SAP

5. Let SNTP adjust QTIME slowly to the "correct" value

Sorry that I don't have access to two sandbox i5/OS systems, even LPARed, to test it myself. And just like anybody else running 24x7 SAP systems, we have been following those SAP notes word by word in the past few years. But waiting for one hour after midnight, with night shifts waiting for SAP to come back, is not fun, isn't it?

Thank you,

Victor

[Former Member]

Victor,

I couldn't agree with you more, under pressure from the business night shifts we once tried a different approach. I can confirm you get some strange messages and a lot of difficulty getting everything back in sync. Things like "SAP IN TROUBLE"! Be ever so careful!!

[Former Member]

Hi Alan,

Thank you very much for the information!

Hope this issue could be fixed in future SAP and/or i5/OS releases.

Thank you,

Victor

[Former Member]

Hello everyone,

Another thought - no every country/state has Daylight Saving Time.

Has anyone used another QTIMZON, like QN0500UTCS, to avoid the downtime? I assume that given enough downtime, SAP can be adjusted accordingly, like ESTNO for system and regular EST for user default in Tcode STZAC. Then in theory, it should only affect sessions/jobs on OS/400 level - one hour difference in the summer time.

No sure of all kinds of interface methods... But for a global organization with servers in different time zones, this issue should have been solved. Any comment?

Thank you,

Victor

[Former Member]

Hello everybody,

the latest news concerning the DST switch can be found in SAP note

> 7417 <

This note should be contacted FIRST in order to obtain information on how to treat SAP systems during the 'double hour' in October. It is always kept up to date with the latest development. From here you can use the 'related notes' in order to drill down to more specific information, like notes 391658 and 697353, which deal with i5/OS.

For SAP customers running a kernel based on 6.40 or higher, SAP note 950114 is of particular interest, because it describes the profile parameter zdate/DSTswitch_contloctime, which is used to control time within the SAP system during the 'double hour'.

Best regards,

B. Wolf

[Former Member]

Vivtor Lin wrote:

Hello everyone,

Another thought - no every country/state has Daylight Saving Time.

Has anyone used another QTIMZON, like QN0500UTCS, to avoid the downtime? I assume that given enough downtime, SAP can be adjusted accordingly, like ESTNO for system and regular EST for user default in Tcode STZAC. Then in theory, it should only affect sessions/jobs on OS/400 level - one hour difference in the summer time.

No sure of all kinds of interface methods... But for a global organization with servers in different time zones, this issue should have been solved. Any comment?

Same question here. Ever got an answer?

[Former Member]

Hello,

When using SNTP the clock is never set backward.

In fact the speed of the clock is slowed down or increased when a time adjustment needs to be made. In iSeries Navigator you are able to see in Configuration and Services -> Time Management -> Time Adjustment if an adjustment is in progress and what time it will take for it to complete.

The daylightchange has in fact nothing to do with the SNTP protocol and as a result of that they are not handled by SNTP.

When have used the SNTP functionality since V5R3 was installed without problems on our system. We are running two SAP instance on our system.

[Former Member]

Hello Mr. Helvoirt,

If QTIME always moves forward, and QTIMZON is not controled by SNTP, how does QTIME behave during time change on V5R3 with SNTP configured?

Could you cut the downtime for backward-time-change from 1 hour to a few minutes?

Thank you very much,

Victor

[Former Member]

Hello Victor,

Assuming that you speak about the Daylightsaving time changes and you use the QTIMZON.

The Daylightsaving time changes are not controlled by SNTP and because of that QTIME is set backwards at the end of the Daylightsaving period. Using a time zone in i5/OS with Daylightsaving the operating system does set the time backwards. In that case SAP should be stopped prior to the time change. In note 102088 there is an official statement from SAP that during daylightsaving changes SAP should be SAP at all times. Note 391658 deals with the Daylightsaving in general on i5 V5R2M0/V5R3M0.

In note 7417 is more documentation dealing with this subject.

From what I have learned from IBM and SAP is that time changes are to be treated with the greatest care. The SNTP server in i5/OS solves this issue, except for the Daylightsaving changes. We do not take any risk and stop SAP twice a year.

Kind regards, Rudi van Helvoirt

[Former Member]

Victor, Please contact me...

Adolfo Rey

adolfo_reyARROBAhotmail....

[Former Member]

Hi Victor,

SAP always runs into issues when you change the clock BACK - and this is more than 1s

So, I would suggest, that setup NTP as described whenSAP is not active => Your iSeries is in sync and then you should update NTP once a day - while SAP is active. This happens on several companies without any issues.

Keep in mind, that this is no solution for the daylight saving time switch. There you need to consult the SAP notes that have several options for you.

Regards

Volker

[Former Member]

Thanks for your quick answer ... but I have some additional questions.

As far as I know, the service for time synchronization under iSeries is the SNTP service, and in its configuration options you can only specify the polling internal, but not when that polling takes place.

So I think we will not be able to control when the update is done, that per your suggestion, it should be done when SAP is stopped (for instance during our night backups).

So, any suggestion on how to control when the time synchronization is done in the SNTP service ?

Thanks, Victor.

[Former Member]

Hi Victor,

that's correct, but what I meant was: Do it THE FIRST TIME when SAP is down ...

So, the following should be run when SAP is down:

CHGNTPA RMTSYS('ntp1.fau.de') AUTOSTART(*YES) POLLITV(720)

(or similar server)

then you might want to restart the NTP service.

Regards

Volker

[Former Member]

Volker, thanks for your answers.

Regards, Victor.