Defining an actor defines the system boundary. Anything that is part of the system we are defining is not an actor. So don't put the database that stores the system information as an actor on the use case diagram: it is part of the system and so cannot be an actor.
|Is always outside the system being modelled|
|Characterises a role of|
|A person, a system or some external entity|
|Linked to one or more system use cases|
|A non-overlapping logical grouping of use cases|
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