Server Downtime, Daylight saving time, and Time Shift

[Former Member]

Dear Experts,

Currently, all our SAP systems are Sandbox systems. Here in Germany, on October 25th, we have a timeshift due to end of Summer Period.

It is mandatory to restart all SAP servers irrespective of their Operating systems.

If restart not performed, does it have any negative influence on systems daily operations, installation tasks and on planned background jobs, after the timeshift?

I found the OSS note: 198411 - Current data and information about time zones, says, to import the customizing data file "tzdata.dat" from report "TZCUSTIM". And again, the same note says, "Customer time zones and daylight saving time are not affected by this, however: they are not overwritten or deleted".

It is absolutely required to do servers restart, in order to get rid of system issues?

Any suggestions, please?

Thanks & best regards,

Sreenu

[yakcinar]

Hello Sreenivasa,

You must check SAP systems' timezone and OS timezone for SAP systems. If they are the same there wont be any problem.

If OS and SAP system timezone DST rule are the same they will behave the same and there won't be any time difference.

If you are chenging OS timezone you must restart SAP system. Chek note 1165982 - Changes to time zone settings at operating system level

"After you change the time zone settings at operating system level, you must restart the SAP application server."

If you change the SAP system's timezone (using STZAC) there could be dumps in your system.

That time you need to restart SAP system.

For summer time rule since DST is adding +1 hour there wont be any problem in timestamps of the records. And if OS and SAP timezone behaves the same there wont be any problem.

For winter time rule since DST takes 1 hour back SAP advices to stop SAP systems before time switch and stay 2 hours downtime and start systems. Check note 102088 - Reducing downtime when changing from summer to winter time

"Ensure that the SAP system is inactive during these "double hours", that is, switch it off an hour before standard time starts for exactly two hours."

If you want you can download and import tzdata.dat (attached to the note 198411 you mentioned) for the most current timzezone settings. But it is not compulsory if your timezone does not change. For example we must import it to our SAP systems since Turkey timezone's DST rule has changed from 25th of Octoberr to 8th of Novemner.

In summary, you must keep SAP and OS timezone synched. They must behave together. If there is difference make them the same and restart the system. When you are changing Os time you must restart SAP. When you are changing SAP timezone you can have dumps and may restart the system. But mostly you donot need to restart.

You can check below link also.

Regards,

Yuksel AKCINAR

[Former Member]

Hello Yuksel,

Thank you for the general information.

But, i don't get exactly, what business impact does it have on systems daily running operations, installation tasks and on planned background jobs, if we don't restart the operating systems?

Best regards,

Sreenu

[yakcinar]

Hello Sreenivasa,

It is not about OS restart. You donot need to restart OS. You just need to make SAP and OS timezones the same.

If there is time difference between your SAP system and OS you will get ZDATE_LARGE_TIME_DIFFdumps and your transaction will not end successfully.

So you would not be able to accomplish your daily work.

There could be communication problems between DB and SAP and you can get connection dumps also.

Bgd jobs will have the same problem.

Regards,

Yuksel AKCINAR

[Former Member]

Hi Yuksel,

Thank you for the informaiton.

I don't understand, why most companies do OS restart during this time switch period? Actually, Operating systems automatically recognize the time changes for summer and winter periods, right?

I assume, OS time interval switches are always syncronized with SAP systems time.

You mean, I have to manually change the OS time intervals?

Best regards,

Sreenu

[yakcinar]

Hello Sreenivasa,

As I said you donot need to restart OS. In my opinion they donot know the issue very well.

The switch times are defined in timezone definition. When that time comes OS applies the rule and add or substract 1 hour to the system time. 

It is the same on SAP layer, too. There are time zone definitions. (Tx STZBC). For those time zones there are DST rules. Whenever the time time comes SAP applies the rule and add or subtract 1 hour to SAP time. You can see time zone definition of an SAP system from STZAC Tx.

OS and SAP behave differently. They change their timez according to the definitionz.

As I said before they must be synchronized I mean the same. If there is difference there is problem.

You donot need to change OS time interval.

1- Just adjust your time zone on OS. Whenever time comes OS automatically adjust it. (As I said before if you are changing OS time you need to restart SAP)

2- Adjust you SAP time zone with the same as OS. It will adjust time switch automatically.

Regards,

Yuksel AKCINAR