What do you mean by atomicity and aggregation?

Atomicity:

Either all actions are carried out or none are. Users should not have to worry about the effect of incomplete transactions. DBMS ensures this by undoing the actions of incomplete transactions.

          Aggregation:

          A concept which is used to model a relationship between a collection of entities and relationships. It is used when we need to express a relationship among relationships.

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Oracle RDBMS