We have about 350,000 portal users who are setup as contacts in Salesforce that we would like to convert to person accounts.
Here are the steps that worked well for non-portal users, but fail for portal users:
- Create a new business account for each of those contacts.
- Update the AccountId for Contacts with corresponding business account created above.
- Change the record type for each account to person account. --> This step throws below exception for portal users.
INVALID_PERSON_ACCOUNT_OPERATION, account cannot be converted to person-account: 
Unfortunately the exception doesn't tell why it failed. Wondering if there a workaround to this? I looked at this and this but they seem to address a standard contact but not a portal contact. And again, we got it to work for standard contacts.