Daylight Saving Time Changes for Database Summaries

The Database process can be set to detect daylight saving time changes and automatically adjust Database Summary intervals after a time transition has occurred. The Database Summary can then summarize 25 hours of data into a 24 hour period, and similarly, summarize 23 hours of data into a 24 hour period.

When a daylight saving time transition occurs, the Database Summary period of Capacity Planning changes from 00:00 - 00:00 to 00:00 - 0:00 + the difference between the GMT offset before and after the transition. For example, if the transition was from +11GMT to +10GMT the Summary would run for the period 23:00 - 23:00.

In the file IRDBASE.INI on Windows and UNIX (or IRDBASEI for HP Non Stop), an option under the [SUMMARY] section controls the automatic adjustment of Database Summary periods that fall over daylight saving transitions:


This option sets the automatic daylight saving transition adjustment to occur only if the source data node is the same as the destination database node.

This option sets the automatic daylight saving transition adjustment to occur when the source database location is either local or remote.

If this field is left blank, or if the NO option is entered, the daylight saving time transition adjustment will be disabled.


a)   Once set, the adjustment of the Database Summary period will only occur when the summary interval is greater than twice the difference in the GMT offsets (before and after transition). For example: a one day summary (24 hours) is greater than two times the difference between a transition from +11GMT to +10GMT (1 hour), so adjustment will occur.

b)   No adjustment will occur if the start time of a summary period occurs before the first (oldest) daylight savings transition, this will often be a period of up to 6 months. For example, if you are summarizing a yearly database that spans more than one daylight saving transition, no adjustment will occur.

c)   By modifying a Display, which shows a Database Summary spanning a daylight saving transition, to show "data time" the correct timestamp will be shown for the interval, for example: for a 00:00 -00:00 daily replay, the first day in GMT +11 will show 00:00 as the timestamp, and then the day after the transition to GMT +10 will also show 00:00. However, the 2nd interval actually contains 25 hours of data. Reports which use the packaged "Capacity Planning" Database Summary should be modified to display "data time".

d)   When GMT is selected as the time type when using the IRDBSCHE utility to specify a scheduled Database Summary, no automatic daylight saving adjustment will occur. In contrast, when LOCAL timestamp is specified (as used in the "Capacity Planning" nightly scheduled summary), adjustment will occur providing the ini file option has been set as either LOCAL or REMOTE and the summary interval is greater than twice the GMT offset difference.

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