SAP Alert
Mark Mergaerts

Daylight saving time starts on 27 March 2016

 22-Mar-2016 21:34:00 by Mark Mergaerts

Logos Alerts are sent out every year before the change to Daylight Saving Time (DST) and the change back to winter time. The current Logos Alert contains the same basic technical information as Logos Alert #21 of March 2015, but has been updated with the most recent data.In 2016 the change to Daylight Saving Time (DST) in Western and Central Europe happens on the 27th of March (Easter Sunday) at 02:00 in the morning (please see the table at the end of this Logos Alert for other continents and regions). DST ends on Sunday, 30 October at 03:00. From an IT perspective the March time change is the “easy” one: clocks go forward one hour, so no “double time” occurs. Nevertheless it is useful to remind you of the rules and recommendations regarding time changes and your SAP systems.

The key SAP note on changes to and from DST is note 7417. The current version of this note dates from November 2011, so there are no major changes compared with last year; however, do check the section Platform-specific and component-specific warnings later in this Alert. The note mostly deals with the much trickier switch from DST back to standard time (“winter time”, also covered by a separate Logos Alert to be sent out in the autumn) but it does raise a few points that you must keep in mind even when the clock goes forward.

 1. BACKGROUND JOBS

All time-dependent activities that are scheduled to run during the “lost” hour (between 02:00 and 03:00 on the Sunday morning) will be affected. This goes first and foremost for background jobs with fixed start times. The normal behaviour is that background jobs will become active when their start time is reached. For example, if a job is scheduled to start at 02:15 and the clock jumps from 02:00 to 03:00, the job will immediately become eligible for running. In most cases this is not problematic, but keep the following situations in mind:

  • When scheduling a job it is possible to set not just the start time but also a “do not run after” time. This could lead to the job being skipped completely. Example: a job is scheduled to run at 02:15 but not to start after 02:45. If the clock jumps from 2 o’clock to 3 o’clock the permissible end time has passed and the job will not run.
  • A job might also start prematurely. Suppose that a job is scheduled to run hourly, starting at 15 minutes past the hour. On the night of the time change it will run at 00:15 and 01:15, but the next run will happen not at 02:15 (which never occurs) but at 03:00. This means that only 45 minutes have elapsed between this run and the previous one, and only 15 minutes will pass before the job runs again at 03:15. Again, such behaviour might be entirely harmless, but it is something to be checked in advance.
  • BI extractors for New General Ledger (NewGL) may run into trouble; see “Platform- and component-specific warnings” below. 

2. TIME CALCULATIONS

The date and time data types in ABAP make it very easy to calculate the distance between two times. The natural tendency is for programmers to use the system-defined values SY-DATUM (current date) and SY-UZEIT (current time) for such calculations. However, these values are time zone dependent and thus cause errors whenever they cross a daylight saving time boundary. The prescribed solution is to use the TIMESTAMP form, which uses Universal Time (UTC) and therefore never jumps forward or backward. ABAP provides the GET TIME STAMP statement for this purpose; calculations with timestamps can be done using the standard object class CL_ABAP_TSTMP. Whereas SAP code uses timestamps for any time-critical calculations, customer or third-party applications do not always follow this rule. If an application critically depends on the calculation of time differences (time registration is an example that springs to mind), then you should be aware of this and take necessary precautions for the night of the time change.

3. TIME DIFFERENCES BETWEEN DATABASE AND APPLICATION SERVER

If you have a distributed system (a SAP system with at least one application instance running on another server than the database server), then you must pay attention to the time settings on the different servers. A database server and all application servers running instances that access this database must always be on the same time zone. In addition  – and this is important for the time change – clock times on the servers should be synchronized so that all servers show the same time. The reason is that while a transaction is executing the SAP kernel checks for time differences between the application and database server. If an important difference is found then the kernel assumes that timestamps used for locking may be compromised, which threatens data integrity. To protect against this the active transaction is aborted and an ABAP dump with keyword ZDATE_LARGE_TIME_DIFF is produced. In such circumstances it is even possible that the SAP application server will shut itself down (see note 1913285).

If a time difference exists between the servers then your system is at risk of hitting this problem. Let’s consider an example: in a distributed SAP system the application server is 15 seconds behind the database server. When the system time on the DB server becomes 02:00:00, the clock on that server jumps to 03:00:00. However on the application server the system time at that same moment is still 01:59:45. At this point a time difference of more than one hour exists between the two servers; it will take 15 seconds before the time jump is made on the application server and the gap is again closed. This implies that there is a 15-second window of vulnerability during which transactions and jobs could abort with ZDATE_LARGE_TIME_DIFF.

SAP strongly recommends connecting all database and application servers to an NTP (Network Time Protocol) service. This seems especially relevant for Windows servers; note 2046718 contains important information about time synchronization with Windows (both on physical and virtual servers) and we advise you to check this note in case you are running Windows-based SAP systems. 

4. IMPORT UP TO DATE TIME ZONE INFORMATION INTO SAP

SAP distributes periodic updates to the time zone customizing data. It is advisable to apply these updates whenever a new version becomes available. The updates are provided as a ZIP attachment to note 198411. To upload the data into the SAP system, run report TZCUSTIM. Note that you must execute this report in all clients, including 000; otherwise there is a risk of transactions failing with the error CONVERT_TSTMP_INCONSISTENT_TAB. 

5. DAYLIGHT SAVING TIME AND JAVA SYSTEMS

For information on how the time change is handled in the SAP NetWeaver Java stack (provided it uses the SAP JVM, which should now always be the case), see note 2232781. 

TO SUMMARIZE:

  1. Identify all background jobs due to run on Sunday, 27 March between 2 AM and 3 AM and ensure that the 1-hour forward time change does not adversely affect these jobs. If in doubt postpone the job until after 3 AM.
  2. Find out with the application owners/key users whether there are applications that are dependent on exact timing or time difference information and determine how these applications should be handled during the night of the switch to DST.
  3. Ensure that clock times are synchronized to sub-second precision between the database server and the application servers (the reason for such high precision is not so much the change to and from DST but rather the risk that in certain situations consecutive timestamps might not be strictly ascending; see note 1740419 for details).
  4. Check the platform- and product specific warnings below to see whether any of these apply to your SAP environment
  5. Import up to date time zone customizing data and execute TZCUSTIM in all clients 

GENERAL INFORMATION AND SUPPORT INFORMATION FOR DST IN THE SAP CONTEXT :

PLATFORM-SPECIFIC AND COMPONENT-SPECIFIC WARNINGS:

  • SAP HANA: possible terminations caused by time difference between application and database server; see note 1932132
  • IBM AIX 5.3, 6.1 and 7.1: various known issues regarding time synchronization and ZDATE_LARGE_TIME_DIFF are known. Please consult notes 1155698 – 1226144 – 1692629 for details.
  • IBM System i: please see SAP note 391658.
  • Windows: issues with time synchronization; please see SAP note 2046718.
  • Business Intelligence (BI), including SAP Business Objects (BO): useful blog on SCN is Daylight Saving Time in BI Platform – 2016 
  • NewGL delta extractor to BI: various problems if extraction runs at the time of the DST change; see notes 1454474 and 1581238

 TIME DIFFERENCE WITH OTHER TIME ZONES:

In case you run an international operation across several time zones or your support organisation is located overseas, then the following table may be helpful to know the time difference between Western/Central Europe and other countries.

NOTE: in the “References” section of SAP note 198411 (the one delivering the updates to the time zone customizing) there is a long list of notes concerning time changes in various countries.

All EU member states

Daylight saving time begins at the same moment regardless of time zone; thus the time difference between countries in the EU always remains the same. This means that in EU states on Central European Time, CET) the clock is set forward from 02:00 to 03:00 local time. In countries on Western European Time (United Kingdom, Ireland, Portugal) the time change is from 01:00 to 02:00. In countries on Eastern European Time (Bulgaria, Cyprus, Estonia, Finland, Greece, Latvia, Lithuania, Romania) the clock goes forward from 03:00 to 04:00.

Norway  (02:00)

Switzerland  (02:00)

Turkey  (03:00)

Non-EU Balkan states  (02:00)

Ukraine  (03:00 – see note)

Like EU; time of change is shown in parentheses

Ukraine: Donetsk region does not observe DST in 2015

Israel

DST starts on Friday, 25 March at 02:00.

Arab countries

Morocco: like non-EU Europe; see above

Jordan: DST starts Friday, 1st April at 00:00

Syria: DST starts Friday, 25 March at 00:00

Other Arab countries do not observe DST.

Morocco

Starts DST on Sunday, 27 March at 02:00
Ends DST on Saturday, 4 June at 03:00 (clock goes back to 02:00)
Restarts DST on Saturday, 9 July at 02:00
End DST on Sunday, 30 October

North America

For full details on DST in the USA and Canada, seehttp://www.timeanddate.com/news/time/usa-canada-start-dst-2016.html

United States:

Daylight saving time began on Sunday, March 13 at 2:00 AM local time. See below for a table of time difference between CET and North American time zones.

The state of Arizona (with the exception of the Navajo Nation Community) does not observe DST. Time difference during European summer time will be -9 (as for Pacific time zone).

Hawaii and US territories, including Puerto Rico, do not observe DST.

Canada:

Daylight saving time began on Sunday, March 13 at 2:00 AM local time, as in the United States.

Most of the province of Saskatchewan does not observe DST. Time difference during European summer time will be -8 (as for Mountain time zone).

Mexico:

In most of the country, including Mexico City, daylight saving time begins Sunday, April 3 at 2:00 AM local time. However, several municipalities on the border with the United States, including various important industrial and commercial centres, change DST in sync with the US (i.e. they began DST on March 13). See http://www.timetemperature.com/tzmx/mexico_dst.shtmlfor detailed information.

Table of time difference between Central European Time and North American continental time zones:

Time zone

Mar 13, 2015 – Mar 26, 2015

(Europe on winter time,

USA and Canada on DST)

Mar 27 – Oct 29, 2014

(Europe, USA and Canada on DST)

Newfoundland

-3 ½

– 4 ½

Atlantic

-4

-5

Eastern

-5

-6

Central

-6

-7

Mountain

-7

-8

Pacific

-8

-9

Alaska

-9

-10

Russia

Does not observe DST.

China (including Hong Kong)

Does not observe DST. Time difference during European DST will thus become 1 hour less (6 hours later than CET instead of 7 hours)

Japan

Taiwan

South Korea

Malaysia

Singapore

Do not observe DST. Time difference between CET and respective countries during European summer time:

·        Japan: 7 hours later than CET

·        Korea: 7 hours later than CET

·        Taiwan: 6 hours later than CET

·        Malaysia and Singapore: 6 hours later than CET

India

Does not observe DST. During European summer time it is 3 1/2 hours later in India than in the CET timezone.

Philippines

No DST

Central America

No DST

South America

In Brazil, most areas changed to winter time on Sunday, February 21 at 00:00. This applies to large parts of the country, including São Paulo, Rio de Janeiro and Brasilia. Winter time ends on October 18, 2015. Northern Brazil and the Amazonas region do not observe DST. For full details refer to the Wikipedia article at http://en.wikipedia.org/wiki/Time_in_Brazil 

Chile did not use DST in 2015 but uses it again in 2016. DST ends and winter time starts on 15 May at 00:00. DST starts again on 14 August at 00:00.

Argentina does not observe DST.

The only other Latin American country to use DST in 2016 is Paraguay (winter time begins on March 27).Uruguay observed DST in 2015 but not in 2016.

South Africa

Does not observe DST. During European summer time the time in South Africa is the same as CET.

Central Africa

No DST

Australia

New Zealand

Australia changes from daylight saving time to winter time on Sunday, April 3 at 03:00 when the clocks are turned backward to 02:00. Western Australia, Queensland and Northern Territories do not observe DST. Winter time ends on Sunday, 2 October.

New Zealand: like Australia, changes to winter time on Sunday, April 3 at 03:00. Winter time ends one week earlier than in Australia, on Sunday, 25 September.

 

KEY SAP NOTES:

Note

Subject

7417

Conversion between standard time and daylight saving time

198411

Current data and information about time zones

319658

iSeries: Daylight saving time/standard time change

1155698

ZDATE_LARGE_TIME_DIFF with AIX 5.3 TL7 SP1 and AIX 6.1

1226144

ZDATE_LARGE_TIME_DIFF with AIX 5.3 TL7,TL8 and AIX 6.1

1454474

0FI_GL_14: Problems with change to daylight saving time

1566014

ZDATE_LARGE_TIME_DIFF

1581238

SAPI supports the daylight saving time change for 0FI_GL_14

1692629

System time may not change properly at DST start/end (AIX)

1740419

Time synchronization of SAP system and time stamps

1913285

Termination ZDATE_LARGE_TIME_DIFF and server shutdown

1932132

SAP HANA : Large time difference between application server and HANA database

2046718

Time Synchronization on Windows

 

 

Topics: time zones