# 6.26. ODPI-C Enumeration dpiSubscrProtocol

This enumeration identifies the protocol used for sending notifications to subscriptions.

Value | Description
--- | ---
DPI_SUBSCR_PROTO_CALLBACK | Notifications are sent by calling the callback specified when the subscription was registered.
DPI_SUBSCR_PROTO_HTTP | Notifications are sent to the URL specified when the subscription was registered.
DPI_SUBSCR_PROTO_MAIL | Notifications are sent by sending an e-mail to the e-mail address specified when the subscription was registered.
DPI_SUBSCR_PROTO_PLSQL | Notifications are sent by calling the PL/SQL procedure specified when the subscription was registered.