Monday, March 14, 2016

Characteristics of real-time database system

What are the characteristics of real-time database system? List the characteristics that define real-time database system clearly, Define the characteristics that differentiate real-time database from conventional database

Characteristics of Real-time databases

  • Data 
    • Temporal data – Type of data whose validity is lost after a specified time. 
    • Dynamic data – data from sensors, archival data, input data to actuators etc. 
    • Static data – as in conventional system
  • Data with time semantics 
    • Data have explicit validity intervals
  • Timing constraints 
    • Response requirements from external world, data are valid for specific time intervals, timing constraints can be on start timings, deadlines or periodic starting etc.
  • Real-time database has to maintain logical consistency and temporal consistency of the data.
  • Predictable response time 
    • If a real-time database transaction misses its deadline it would cause serious implications. Hence to avoid it the response time should be predictable in most of the cases.
  • Real-time transactions 
    • Transactions with ACID properties supported. 
    • In few cases 
      • atomicity can be relaxed, 
      • isolation may not be needed always, 
      • serializability can be relaxed, and 
      • not all data are durable.
  • Correctness of the data 
    • Integrity of the data is required. In few cases correctness can be traded for timeliness.
  • Efficient access to the data
  • Performance metric 
    • Real-time database is evaluated based on calculating the number of transactions missing their deadlines.
  • Priority scheduling 
    • Transaction processing in a real-time database should be based on priority and criticalness of transactions.

An effective real-time database system needs to be able to handle time-sensitive queries, return only temporally valid data, and support priority scheduling.



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