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In an Ibor or Agent, in the 'Destinations' tab you can set the 'Specific Devices' However, it is a Device or Delivery Profile the one used for alerts, see this OBIEE guide:
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User's Guide
https://download.oracle.com/docs/cd/E21764_01/bi.1111/e10544/toc.htm
https://download.oracle.com/docs/cd/E21764_01/bi.1111/e10544.pdf
page 218
What Are Devices and Delivery Profiles?
Devices and delivery profiles control how you will be reached when an alert is
generated by an agent and which devices receive the content:
¦ Device — A device is the medium used to deliver content to you. The content of
an agent can be delivered to a range of devices as an e-mail or SMS message.
¦ Delivery profile — A delivery profile specifies which devices to use to deliver
content to you, based on the priority of the content. You can define several
delivery profiles to meet your needs, and switch
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