Adabas Database overview

ADABAS -   Adaptable Data Base System.

Adabas is more flexible than hierarchical and network and very close to relational. Pseudo-relational DBMS stores the access path to the database rather than creating them for each request.

Database concept solves the problem of

·        Duplication of Data

·        Needing to know the exact file structure

·        Programs to be changed when data’s are organized differently

Goals

·        Increase data Independence

·        Reduce data Redundancy

·        Maintain data Integrity

·        Increase data Security

Data compression

 Adabas has the option to store data in a disk in the compressed form. This helps to reduce the disk space and I/O operations

•         Leading zeroes are removed from Numeric Fields

•         Trailing spaces are removed from Alphanumeric fields

•         Null value fields are compressed to a single byte

•         Numeric data is packed

Architecture

·        Associator  -  Contains information about the entire database

·        List of all Adabas dataset in the database

·        Physical location of the dataset (Block number)

·        Descriptions of all fields in the Field description table

·        Inverted list for each descriptor

·        Address converter for relative record location

There is one address converter for each dataset in the database

·        Is the index to the physical storage location

·        One address converter for each data set

ADABASic process

Adabas Data Access

• READ

• Labels

· *ISN

· FIND

· *COUNTER

· GET

· STORE

· UPDATE

· DELETE