SID is the enterprise identification and authentication account at SHC to access its systems and applications. It has no relation and no interaction with Stanford SUNet ID. For clinicians that are employed by the University, they don't get SIDs automatically as the SHC employees do.
To obtain a SID for employees in the Department of Medicine, you first need to contact your division manager who in turn will use an online request form at medicine.stanford.edu/shc to make that request.
With SID, you can further request access to other systems such as Epic, remote secure token, etc.