Just saw this and thought I would add the time zone question to the equation.
I've always deployed a sufficiently robust (HA and plenty of great database syncronization) a single "Data Mart" that has its data pulled from ODSs located at all of the different sites. Only one ODS (Operational Data Source) per time zone is required.
Make sure that you assign the correct time zone when defining ODSs to the Data Mart (using ETL Assistant). You cannot change this assignment after initial entry. Any report that any site runs on any object across any time zone will be displayed in that site’s time zone. We always keep all of our servers on UTC (GMT..kind of) so when we generate reports presented in a particular time zone , we customize the selection criteria derived from time fields that are not GMT-based, in each of the desired canned reports, to hold the equivalent values of the time zone on which you wish to generate reports.
And this is a Genesys description of how to adjust the times:
"Wherever search criteria is used in each of these reports (such as specifying the date range on which to generate the report), each non-GMT based time field used in that search criteria would have to be converted to the appropriate time zone value. For instance, where search criteria are derived from BEGIN_TIME, you might substitute NEW_TIME(BEGIN_TIME_GMT,’GMT’,’CST’) using the Oracle NEW_TIME function to convert BEGIN_TIME to its Central Standard Time equivalent. Criteria may involve any time-related fields for which GMT, generally, does not appear in the column name, such as ADD_TIME, BEGIN_TIME, DELETE_TIME, END_TIME, OBJ_ADD_TIME, and OBJ_DEL_TIME."
