We're running an Oracle Database as Policy Store and we'd like to know
if we have to register again the Policy Server to the Policy Server
Oracle new database ? If yes, how should we do this ?

Policy Server 12.7SP2 on RedHat 6;

At first glance, you only need to move data from 1 Oracle data base to
the other and modify the connection data to the new Policy Store.

Further documentation :

  How to Configure an Oracle Policy Store
  https://techdocs.broadcom.com/content/broadcom/techdocs/us/en/ca-enterprise-software/layer7-identity-and-access-management/single-sign-on/12-8/installing/install-a-policy-server/configure-odbc-databases-as-policy-session-key-and-audit-stores/configure-an-odbc-database-as-a-policy-store/how-to-configure-an-oracle-policy-store.html

  Step 3: Replicate the Policy Store
  https://techdocs.broadcom.com/content/broadcom/techdocs/us/en/ca-enterprise-software/layer7-identity-and-access-management/single-sign-on/12-8/upgrading/parallel-upgrade/step-3-replicate-the-policy-store.html