Sequential or Serial File Organization
i)Data records are arranged one after another.
ii)Records are arranged and accessed in a predetermined order of their keys.
iii)Definite relationship between logical and its physical organization.
iv)Magnetic tape is the storage medium.
v)Linear search algorithm can be used to access the records.
Advantages :
i)Continuous and simple.
ii)Can be used for data processing.
iii)Record key can be used to access the data.
iv)Cheaper storage medium(Magnetic tapes)
v)Localized errors.
Disadvantages :
i)Doesn't suit for random file organization.
ii)Cannot be for low activity rate.
iii)Possible only with batched and sorted data.
iv)High data redundancy.
Direct or Random File Organization
i)Data records are placed in a random order.
ii)Related records are separated physically.
iii)Magnetic disk is the storage medium.
iv)Hashing algorithm can be used to access the records.
v)Hashing function generates a physical storage address for a particular record key.
vi)Conflict resolution technique solve the conflicts.
Advantages :
i)Saving Storage space - no index is used.
ii)Fast access - mapping exists between record key and its physical location.
iii)Saving time - no sorting for add,delete,update.
iv)Flexibility - Both sequential and non-sequential arrangement.
v)Effective online processing.
Disadvantages :
i)Detailed programming
ii)Less efficient in the usage of storage space.
iii)Difficult file update.
iv)Costlier storage medium(magnetic disk)
v)can be implemented only with direct access devices.
Indexed Sequential Access Organization
i)Combine the features of serial and direct file organizations.
ii)Data records storage are random and their access is sequential.
iii)Can also be called as ISAM(indexed sequential access method).
iv)Has main file storage and an index table.
v)Binary search algorithm is used to access the records.
Advantages :
i)combines sequential and direct access.
ii)Suit for the files which has both sequential and direct access.
iii)Quick access is possible with high activity ratio , large no.of records , arranged index table.
Disadvantages :
i)Expensive special software and hardware.
ii)Extra processing time for index.
iii)Extra storage for insertion.
iv)Slow retrieval when compared to random access.
2. Data Consistency
3. Data Integration
4. Data Sharing
5. Enforcement of standards
6. Application Development Ease
7. Better Controls
8. Data Independence
9. Reduced maintenance
i)Data records are arranged one after another.
ii)Records are arranged and accessed in a predetermined order of their keys.
iii)Definite relationship between logical and its physical organization.
iv)Magnetic tape is the storage medium.
v)Linear search algorithm can be used to access the records.
Advantages :
i)Continuous and simple.
ii)Can be used for data processing.
iii)Record key can be used to access the data.
iv)Cheaper storage medium(Magnetic tapes)
v)Localized errors.
Disadvantages :
i)Doesn't suit for random file organization.
ii)Cannot be for low activity rate.
iii)Possible only with batched and sorted data.
iv)High data redundancy.
Direct or Random File Organization
i)Data records are placed in a random order.
ii)Related records are separated physically.
iii)Magnetic disk is the storage medium.
iv)Hashing algorithm can be used to access the records.
v)Hashing function generates a physical storage address for a particular record key.
vi)Conflict resolution technique solve the conflicts.
Advantages :
i)Saving Storage space - no index is used.
ii)Fast access - mapping exists between record key and its physical location.
iii)Saving time - no sorting for add,delete,update.
iv)Flexibility - Both sequential and non-sequential arrangement.
v)Effective online processing.
Disadvantages :
i)Detailed programming
ii)Less efficient in the usage of storage space.
iii)Difficult file update.
iv)Costlier storage medium(magnetic disk)
v)can be implemented only with direct access devices.
Indexed Sequential Access Organization
i)Combine the features of serial and direct file organizations.
ii)Data records storage are random and their access is sequential.
iii)Can also be called as ISAM(indexed sequential access method).
iv)Has main file storage and an index table.
v)Binary search algorithm is used to access the records.
Advantages :
i)combines sequential and direct access.
ii)Suit for the files which has both sequential and direct access.
iii)Quick access is possible with high activity ratio , large no.of records , arranged index table.
Disadvantages :
i)Expensive special software and hardware.
ii)Extra processing time for index.
iii)Extra storage for insertion.
iv)Slow retrieval when compared to random access.
10.12 INTRODUCTION TO DBMS :
Definition : Management ,
maintenance and retrieval operations of data in a database.
Advantages :
1.
Less
Data Redundancy –
i)With
a centralized data base , various programs can access data in different data
files.
ii)Need
not be duplicated.
2. Data Consistency
i)Complicated
operations will be avoided.
3. Data Integration
i)With a centralized data base , easy
integration with minimum programs.
4. Data Sharing
i)With a centralized data base , data can be shared across the application.
5. Enforcement of standards
i)Easy because of single set programs.
6. Application Development Ease
i)Easy
because the developer need not consider about concurrent access , integrity ,
security.
7. Better Controls
i)Because
of centralized data base.
8. Data Independence
i)Three
level architecture.(internal, conceptual, external).
ii)Operations
at one level doesn't affect other levels.
9. Reduced maintenance
i)Easy
because of centralized data base.
No comments:
Post a Comment