ACID Properties of Transaction in DBMS refers:
Atomicity: Atomicity in ACID Properties of transaction means never partial execution is done.
Isolation: Isolation in ACID Properties of transaction means program or process never depends or effects any other program or process during execution.
Durability: Durability in ACID Properties of transaction means changes by a transaction is durable till other transaction doesn’t change it.
Consistency: Atomicity, isolation and durability all are found during transaction, it means database have consistency.
Program: Combination of instructions is called program.
Instruction: It is atomic in nature and certainly never partially execute.
Process: In short, Execution of program is called process.
Transaction: on the other hand, Transaction is a program or process or set of instructions which perform a logical unit of work.
Problems of Concurrency Transaction:
- Dirty read problem
- Unrepeatable read problem
- Phantom read problem
- Lost update problem or Write-Write conflict
Active State: All instructions of a process or transaction is execute in active state of Transition States.
Partially Committed: After execution of all instructions, changes are further temporarily store in buffer or main memory.
Committed: Changes are further permanently store in database.
Solution of Concurrency Transaction Problems: Scheduling
1. Serial Schedule: In Serial Schedule one transaction is completed then another transaction is started.
That is to say, In between a transaction of serial schedule, any other transaction doesn’t occurs.
Therefore, In Serial Schedule context switching doesn’t occurs.
This schedule will be safe for a transaction and also it will always consistence.
2. Non-Serial Schedule: In Non-Serial Schedule context switching occurs in between a transaction.
Consequently Non-Serial Schedule is unsafe for a transaction.
Therefore, Scheduling management is needed for Non-Serial Scheduling.
1. If we convert Non-Serial Schedule into Serial Schedule by swapping of non-conflict instruction then this schedule is known to be conflict serializability.
2. If a schedule is not recoverable, certainly it means this schedule is not scheduled in database.
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