Linda, from Nike has raised a valid observation i.e. "When we upgraded to 11.3.6 SP4 it wipes them [time zones] out, and it's a manual process to add them back in."
We have had the same issue when applying a "cumulative" to an existing instance [11.3.5 with ORA].
Having the time zones wiped out by an application of a "cumulative" or with an upgrade, depreciates AE.
Is there a ready fix and/or a workaround ?
A process that would backup the timezones before the upgrade, then report on differences and provide a quick and easy (and accurate) way to add back missing timezones would be really nice as well.