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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