Object-Oriented Database System Properties

---

Persistence
Persistence is the data or objects on which the user or programmer works survive the execution of a process and can be used again in other processes.

Suppose the initial value of J is 1. J = J + 1 is a line of code in a program. The new value would be automatically saved to persistent storage, and when the program was executed again it could access the saved value. After executing the program twice, the new value of J is 3.

Multi-user Control

• Transactions control: A transaction is a logical unit of work; that is, it must be entirely completed or aborted—no intermediate ending states are accepted. All transactions must have the following properties:
  
  

  Atomicity Durability

  Serializability Isolation



• Concurrency control: A DBMS feature that is used to coordinate the simultaneous execution of transactions in a multiprocessing database system while preserving data integrity.

Recovery
When an error occurs which corrupts the content of the database buffer, the system must be able to restore a consistent state.

Secondary Storage Management
In database systems data is stored on secondary storage media, and sophisticated functionality is provided to access data and transfer it between main and secondary storage. These techniques deal with, for example, index management, the clustering data, buffer management, access path selection and even query optimization.