How is persistence handled in typical OO database systems?

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There are two methods that the OODBMS uses to access persistent objects, virtual memory address pointers, and hash tables. A persistent object will always be ready to be invoked, and its state can and will be preserved and survive any kind of system failure. Remember, persistent objects are stored on disk and transient objects exist in RAM memory.  In an OODBMS, an object may traverse between states.

 Persistent means that the object has been saved to the database whereas transient means that it hasn't been saved yet. So for example when you get an entity from a repository, that entity is persistent. When you create a new entity, it is transient until persisted.



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