Changing anchor SQL management Agent

We have SQL Management agent used for creating accounts in AD/LDAP.

Achor is Accountname , we generate it based on Fname and lname when a record is added to SQL.

Join is AccountNumber ( which is another unique entry)

Now we want to change Anchor for SQL to some other attribute in SQL-  we want to use column number as a new anchor.

My understanding is if we change anchor , it will generate a record in FIM for all the objects present.

Any suggestion or steps for changing anchor for SQL  without affecting current users in SQL / AD ?

AdiKumar