Need some advice in Azure AD tenant to tenant Migration. ( Not sure if this is available within Microsoft)
Aim: Migrate selected users/groups from one AD to new AD. It's a divestiture Migration scenario. Eg. Company ABC corp have one single AD consist of users from AAA and BBB companies but now they are separating. BBB going for his own AD and environment.
Existing Setup: Hybrid Azure AD Environment, Single AD forest.
Following is the approach consideration:
1. Migrate only selected user from source AD to target AD. (On-Premises AD)
2. After users got migrated to target AD. Setup AD connect and sync these users from target AD to Azure AD.
Let me know if the above approach is right or not , also any advice on best practices to achieve this scenario.
Also I got few doubt after migrating users from source to target AD. At what stage I need to move Custom domain from Source Azure AD to target Azure AD at very beginning or need to do this in the end ? What I'm thinking if we do batch-wise migration so we need to still keep the custom domain in source tenant till we completely migrate all selected users. But thinking if we didn't do this in the beginning then user sync via AD connect from new target on-prem AD to new Azure AD would fail because user in on-prem AD got custom domain in his UPN and email but when syncing to new Azure AD it's missing.
In case if we don't add custom domain then user would change to **.onmicrosoft.com* domain and later we can add it to new Azure AD tenant and we will change primary domain for all users.