Multiple domain aliases
If your organization has multiple domains and/or multiple email aliases for user accounts, these email addresses should be provisioned on the user account in Google Apps before migrating Calendar data. If these aliases are not defined in Google Apps, Calendar event data may not be properly reflected or migrated to Google Apps.
Calendar event modifications not migrated for migrated events
Calendar migration does not support migrating delta changes to existing events that have already been migrated to Google Apps. For example if the details of a meeting are updated after migrated to Google Apps even if you configure the migration tool to “Migrate all data (overwriting previously migrated data)” these events are not be updated. Because of this, consider carefully when best to migrate Calendar data. Calendar migration does not support a date range for migration.
The Calendar migration will pick up new meeting requests created since your last
migration, as with contacts and email.
When migrating contacts, if you remigrate and choose “Migrate all data (overwriting previously migrated data)” duplicate contacts will be created in Google Apps. If this occurs, the user can use the “Find Duplicates” option in Google Apps contacts to merge duplicate contacts.
The contact migration tool will migrate new contacts created since your last migration, but does not migrate contacts that have been modified since the last migration.
Running a migration from the command line
For details on how to do this, see the help center article Run GAMME from the command line: http://support.google.com/a/bin/answer.py?&answer=2790147