Updating thousands of records SMAX

Hello,

We received a request from our customer to hide all the records for a specific group so they can see only the records that are assigned to them, but all our records are public (have data domain as 'Public') and we need to update all the records from data domain 'Public' to something else, the problem is that we have more than 90 000 records and we can only update around 200 record per API,

 was thinking about making a rule in the 'Per schedule' business rules that change automatically the data domain of the records but it is a high risk since it will apply to all the records at once and server may go down,

Do you guys have any suggestion ? I

Thank you in advance,

Kind regards.