Attribute Sync in Sailpoint means to sync the attribute value to target application.
In SailPoint IIQ, whenever any attribute value is updated, we need to change the old value in target application with the updated value. This is called Attribute Sync in Sailpoint IIQ.
Attribute Sync setting is done on the same page of identity mapping (read more on identity mapping).
Instead of Add source, we have to select Add target as we have to update value at target source.