File processing system with example

Answer 1

A file processing system is a collection of files and programs that access/modify these files. Typically,

new files and programs are added over time (by different programmers) as new information needs to be

stored and new ways to access information are needed.

Problems with file processing systems:

• data redundancy and inconsistency

• difficulty of accessing data

• problems with concurrent access

Example: assume I'm paying for groceries with my MAC card at the same time my pay check is being

deposited (and my bank uses a file processing system):

a.)withdrawal program deposit program

1. read balance from checking account

file as $51

2. read balance from checking account file as $51

3. subtract $50 (for groceries)

4. update checking account file

(new balance: $1)

5. add $100 (my salary)

6. update checking account file (new balance: $151)

It is difficult to prevent such problems unless programs (example: withdrawal and deposit) are coordi-

nated or integrated.

b.)atomicity problems - ensuring that a system failure during a database update does not leave the

database in an inconsistent state

c.)security problems

- not all users should have access to all data

- example: bank payroll personnel shouldn't know my checking account balance

- difficult to enforce security in an ad hoc system

d.) integrity problems

- data may need to satisfy certain conditions, called consistency constraints

- example: account balances should never fall below $0

- difficult to enforce/add/change consistency constraints in a file processing system

DBMSs were developed to remedy these problems.