transactionprocessingppt-171212112608.pptx
- 2. Contents 1. DEFINITION . 2. EXAMPLE. 3. PROPERTIES. 4. TYPES. 5. WORKING. 6. LONG DURATION TRANSACTIONS. 7. ADVANTAGES & DISADVANTAGES. 8. LONG DURATION TRANSACTIONS.
- 3. DEFINITION A transaction can be defined as group of tasks. A single task is the minimum processing unit which cannot be divided further. It is an action, or series of actions that are being performed by a single user or application program, which reads or updates the information. A transaction processing system (TPS) is a type of information system that collects , stores, modifies & retrieves the data transactions of an enterprise.
- 4. Example Of A Transaction In DBMS Suppose a bank employee transfers Rs 500 from A's account to B's account. This very simple and small transaction involves several low-level tasks. A’s Account Open_Account(A) Old_Balance = A.balance New_Balance = Old_Balance – 500 A.balance = New_Balance Close_Account(A)
- 5. Continue… B’s Account Open_Account(B) Old_Balance = B.balance New_Balance = Old_Balance + 500 B.balance = New_Balance Close_Account(B)
- 6. PROPERTIES OF TRANSACTIONS There are properties that all transactions should follow & possess. The four basic are in combination termed as ACID properties. The ACID has a full form & is as follows: 1. ATOMICITY: Atomicity means that a transaction is either completed in full or not at all.
- 7. Continue… For example, if funds are transferred from one account to another , this only counts as a bone fide transaction if both the withdrawal & deposit take place. If one account is debited & the other is not credited, it does not quilify as a transaction. TPS systems ensure that transactions take place in their entirety.
- 8. Continue… 2. Consistency: TPS systems exist within a set of operating rules (or integrity constraints). If an integrity constraint states that all transactions in a database must have a positive value, any transaction with a negative value would be refused. 3. Isolation: Transactions must appear to take place in isolation. For example, when a fund transfer is made b/w two accounts the debiting of one & the crediting of another must appear to take place simultaneously. The funds cannot be credited to an account before they are debited from another.
- 9. Continue… 4. Durability: Once transactions are completed they cannot be undone. To ensure that this is the case even if the TPS suffers failure, a log will be created to document all completed transactions.
- 10. TYPES OF TPS There are two types of TPS: 1. Batch Processing 2. Real Time Processing. 3. Batch Processing: • Batch Processing is where the information is collected & stored as a batch but not processed immediately. • Batch processing is useful for enterprises that need to process large amounts of data using limited resources.
- 11. Continue… Example: Payment by cheque, Credit card transactions, etc. 2. Real Time Transaction Processing: • Real Time Transaction Processing as the immediate processing of data with the database updated as the transaction is being carried out. • Mostly in Online shopping.
- 12. Continue… Example: Bank ATM & POS terminal( Point of sale terminal) , both of which have user input which requires immediate feedback.
- 13. Working Of TPS
- 14. Advantages & Disadvantages Of TPS Advantages: 1. Batch or Real Time Processing available. 2. Reduction in processing time, lead time & order cycle time. 3. Reduction in inventory, personnel & ordering cost. 4. Increase in productivity & customer satisfaction. Disadvantages: 5. High setup costs. 6. Lack of standard formats. 7. Hardware & software incompatibility.
- 15. Long Duration Transactions Traditional concurrency control techniques do not work well when user interaction is required: Long duration: Design edit sessions are very long Exposure of uncommitted data: E.g., partial update to a design Subtasks: support partial rollback Recoverability: on crash state should be restored even for yet-to-be committed data, so user work is not lost. Performance: fast response time is essential so user time is not wasted.
- 16. Continue… Represent as a nested transaction atomic database operations (read/write) at a lowest level. If transaction fails, only active short-duration transactions abort. Active long-duration transactions resume once any short duration transactions have recovered. The efficient management of long-duration waits, and the possibility of aborts. Need alternatives to waits and aborts; alternative techniques must ensure correctness without requiring serializability.
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