This document discusses transaction processing systems (TPS). It defines a transaction as a group of tasks that updates or retrieves data. A TPS collects, stores, modifies and retrieves enterprise data transactions. Transactions must follow the ACID properties - atomicity, consistency, isolation, and durability. There are two types of TPS - batch processing, which collects and stores data in batches, and real-time processing, which immediately processes data. Long duration transactions pose challenges as user interaction is required and partial data may be exposed if not committed. Nested transactions and alternatives to waits and aborts can help manage long-running transactions.

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)

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 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.

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 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.

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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.

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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.
1. 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.

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 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.

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 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:
1. High setup costs.
2. Lack of standard formats.
3. 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.

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 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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