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Databases for real time systems are meant for the use of both hard and soft systems. Since hard real time systems needs strict timing constraints, conventional disk based databases are not suitable, but soft real time systems makes use of disk based systems through FCFS, Elevator or scan policy algorithm.
There should be some solution for [...]

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In disk based scheduling, the disks are located and traced by traversing the sectors and tracks. Tracks are concentric circles and sectors are just originating from the center of the disks.So, disk scheduling algorithms are slower when compared with the memory based scheduling. Under disk based schedulingTa=Tw+Tp+TtTa is the access timeTw is the time spent [...]

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Pessimistic Concurrency Control

The transactions are been checking for violating the serialization consistency before letting it execute is called pessimistic concurrency control

Two phase locking Scheme

Read /Write lock as a phase
Unlock – another phase
Both the above phases wont interleave, because of this, there may be deadlock, which can be detected by means of deadlock [...]

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Transaction Abortions
Transaction abortion is of two types, either

Termination abortion or

The Transaction which is aborted in this way won’t be restarted
Example: An attempt to divide by zero error

Non Termination Abortion

The transaction which will be restarted after it is being aborted
Example: data conflict due to a deadlock, If two transactions are involved in a deadlock, [...]

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Transaction Priorities

Transactions are granted access to the processors based on their priorities.
All the transactions in the real time DB are associated with a deadline, hence Earliest Deadline First (EDF) algorithm finds a greater solution to schedule those transactions. But EDF algorithm will be working efficiently if the number of transactions are moderate. But usually [...]

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Main Memory Databases

The entire database is residing on the main memory is the concept behind main memory databases. But there are some problems like data backups and storing logs. So Main memory databases are to rely on Disk based systems to store logs and backups.
General purpose databases are really huge to sit in to [...]

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The queries associated with a Real time databases are associated with a deadline, there may be some response after the queries passed the deadlines.
The data returned in response to a query must have absolute and relative consistency.
 
Absolute Vs Relative Consistency
Absolute consistency is accuracy. The data returned in response to a query must be close [...]

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Transaction
It is said to be set of read or write operations
Query
A Transaction is said to be a query if it contains either a read or update operation
 
Commit is a point of no return, once a transaction is commited we are certain that, the changes to the database are permanent
 
ACID Properties of a General Purpose [...]

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