How to maintain managers in GRC without any HR org structure in ECC?

Hi,

We are planning to use SAP Access management in GRC 10, we would like to have manager approval in the access provisioning workflow.

As we do not have Manager's maintained in the ECC/GRC, we would like to maintain a custom table in the GRC which has the manager mapping and use that table for the population the manager field in GRC application.

Also as part of this, we are trying to figure out, where is the manager stored for a user in GRC?

thank you in advance.

Pranay