Warning notes are used when the user must be notified about something that may require action. They have a fairly long duration, and a sound that can be heard (and distinguished) even when not concentrating on the phone. For example, the battery low warning.
You can create either a basic warning note that is displayed only when your application is in the foreground or a global note that stays displayed even if the application launching the note is not in the foreground. The related APIs are the Notes API (for basic notes) and the Notifiers API (for global notes).
To use a warning note with the default icon, text, sound, and duration, create an instance of the note class CAknWarningNote.
To create a global warning note, use the class CAknGlobalNote in the Notifiers API. For implementation information, see Using global notes and Using global notes with user interaction.