Storage and retrieval: Processes by which data and information is saved and accessed later

• DBMS provides secure, reliable and effective methods for storing and retrieving

Database Management Systems including(DBMS):

The role of a DBMS in handling access to a database

DBMS → software package that allows users to access a database so they can manipulate, and store and retrieve data there

• In a DBMS, the data is organised into tables, viewed in forms, retrieved w/ queries & displayed in reports.
• DBMS manipulates data in many ways i.e. searching & sorting
• DBMS provides security measures by restricting access:
  • Record Locking: Locking a record when user accesses it, preventing anyone other than original user from accessing
    • i**.e. someone makes 2 transactions and 2 participants try to make 2 different edits to the same empty record at the same time so one transaction is not processed/identified**
  • Levels of Access: Depends on user accounts and how much access they are authorised
  • Password protection: Passwords stop unwanted people from getting in
• DBMS also helps users develop + maintain a database in many ways:
  • organises data w/ a data dictionary
  • shows relationships between entities using schematic diagrams
  • checks for identifiable errors in data entry
  • provides information about the performance of the database.

The independence of data from the DBMS

• NOTE → database is the storage of data, DBMS provides access to the data
• data is independent from DBMS (it’s just software, it has none of the actual data)
  • if DBMS is changed (e.g. software updates), data is unaffected and vice versa
• Microsoft Access is a DBMS that allows users to access, manipulate and enter data in the Microsoft Jet Database Engine

Direct and Sequential Access of Data

• Sequential Access → the data is accessed in a sequential and methodical manner
  • data is retrieved by starting at the beginning of the tape & reading all data until required item is found (like going down dictionary from start until u find one specific word)
  • much slower than direct access & impractical when immediate processing is required
• Direct access → when the software knows the exact location of a data item and can access directly. An example of this is HDD and SSD.
• indexed access → direct access through the use of an index
  • index → table that contains info about the location of data
  • data accessed by referring to index and gaining its exact location
  • requires additional processing time to search + maintain index
  • indexed access is widely used to store data on disk & data in a database

Centralised and Distributed Databases

Distributed Databases → a database located at more than one geographical site

• acts as a single collection of data but is geographically dispersed