Hi Chandra,
To enable attribute synchronization, it is mandatory that the attribute is configured as an Identity Attribute. This is because the concept of attribute synchronization is to maintain the data from the Identity Cube as the source of truth to be propagated across connected sources.
Attribute synchronization ensures that account data on a source remains consistent with identity data in Identity Security Cloud. It uses identity information to keep data aligned across multiple systems in your enterprise.
Refers to Attribute Sync for more info.