How to reduce the downtime when changing from daylight saving time to winter time from a little over two hours, to a little over one hour.
You search for information about the operation of SAP systems during the time conversion from daylight saving time to winter time.
Problems occur at the end of daylight saving time (within a period of an hour, for example from 2.00 a.m. to 3.00 a.m.) such as runtime errors "ZDATE_LARGE_TIME_DIFF", "ZDATE_ILLEGAL_LOCTIME", "ZDATE_ILLEGAL_DBTIME".
These may appear only in the system log or as messages in the status line.
At the end of daylight saving time, there is a time interval (generally precisely one hour) that occurs twice ("double hour").
Applications working in local time have a general problem with the "double hour." The time does not run constantly for them, and a point in time may occur twice.
Within the SAP kernel, problems occur that are related to C-runtime library functions. If these receive a local time in the "double hour," they must decide whether to adopt daylight saving time or standard time. The decision they make depends on the platform and the local time zone.
For the reasons stated above, problems can also occur with the SAP system in this "double hour".
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.
In Germany, for example, daylight saving time ends around 2:59.59 a.m and the standard time starts with the next second at 2:00.00 a.m. Deactivate the system for two hours from 2:00 a.m. (daylight saving time) until 3:00 a.m. (standard time).
Shutting the system down for two hours is usually sufficient. For heterogeneous system landscapes, and if you are not sure when your servers are switching from daylight saving time to standard time.
For some operating systems, there is additional information. Refer to the list of related notes below.
You can reduce the period the system is switched off to the amount of the daylight saving time offset (in the above example from 2 to 1 hour). The prerequisite is that all processes involved in the SAP system have technically identical local time settings. If this is the case, you must find out when standard time starts on your system. Use a utility program to do this: The program is called "endofdst" and has been attached to this Note.
Run the program in the same environment in which you run the SAP system processes (identical local time zone). The program specifies the time when you should deactivate your system for a little over an hour.
If you are using kernel 6.40 or higher, you need to set the following profile parameter :
zdate/DSTswitch_contloctime = off
You should use transaction RZ11 to dynamically switch the profile parameter in the active system before the "double hour".