As a "basic" overview:
The BBDBUpdate updates the Blackberry database so it is aware of the new DST start and end dates of affected time zones. Also by running this update it will automatically correct existing calendar entries (on the device) and ensure new entries are set to the correct time (technically the correct GMT offset amount). The reason why you need the handheld patch is to ensure that the Blackberry device is also aware or able to accept these time zone changes.
Here is a sample line from LoadSyncDeviceConfig.sql
Code:
UPDATE SyncDeviceConfig SET Data = '<R15403><TZID>255</TZID><ZoneStringID>Australia/Sydney</ZoneStringID><GMTOffset>600</GMTOffset><DSTAmount>60</DSTAmount><DSTStartMode>1</DSTStartMode><DSTStartMonth>9</DSTStartMonth><DSTStartDOW>1</DSTStartDOW><DSTStartDay>1</DSTStartDay><DSTStartTime>120</DSTStartTime><DSTEndMode>1</DSTEndMode><DSTEndMonth>3</DSTEndMonth><DSTEndDOW>1</DSTEndDOW><DSTEndDay>1</DSTEndDay><DSTEndTime>180</DSTEndTime></R15403>'
WHERE SyncDbTypeId = 15403 AND TableId = 1 AND Guid = 40
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