Sunday, March 13, 2016

Misconceptions about real time databases

Misconceptions about real-time databases, What cannot be considered as the real-time databases? Some false information that would lead people to have a wrong understanding on what is real-time database.

Misconceptions about real-time databases

Real-time database is sometimes understood mistakenly by many people as follows; actually real-time does not mean fast, or main memory etc.

  • Advancement in the hardware technologies will address the requirements of real-time database 
    • The improvement in hardware technologies alone cannot make a difference. Hardware improvement has nothing to do with timing constraints of real-time transactions.
  • Advancement in database technology can address all the real-time database requirements 
    • Improved buffering mechanism, faster commit protocols and state-of-the-art query processing techniques cannot guarantee the deadlines to be met by a transaction or temporal validity of data in a real time database.
  • Real-time computing is fast computing 
    • Real-time databases aim to meet the timing constraints and data-validity requirements of individual transactions and also keep the database current via proper update rates. This just cannot be achieved with fast computing property.
  • All the real-time database requirements can be handled by traditional databases 
    • Traditional databases cannot be as efficient as the one real-time database built from scratch for the real-time applications.
  • Placing the conventional database in main memory is equivalent to real-time database 
    • Placing database in main memory cannot solve this real-time issue. Conventional databases still have many additional sources of unpredictability such as delays due to blocking on locks, transaction scheduling, stolen processing time to handle external interrupts, and so on.
  • A real-time database is one which resides totally in main memory only 
    • Need not be. Placing the real-time database in main memory will definitely increase the speed of the system. But, we may need to deal with some non-critical disk-resident data as well.
  • A temporal database is a real-time database 
    • Temporal database deals with the time associated with information whereas real-time database deals with satisfaction of timing constraints with respect to operational aspects. Temporal database may store time based durable data, but real-time database stores time based data with timing constraints like when the data is valid.
  • Real-time database cannot achieve predictability 
    • This may not be completely true, because in cases like specialized real-time transactions (for example, updating periodic sensor data) or fixed real-time transactions (for example, using the same type of data or amount of data each time) they are predictable.

Reference: John A. Stankovic, Sang Hyuk Son, Jorgen Hansson, “Misconceptions about Real-Time Databases,” IEEE Computer, 2009



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