Appendix C

1
Appendix C

• File Organization Storage Structure

2
Agenda

• Definition
• Types of Storage
• Types of File Organization

3
Definition

• Logical record physical record
• File organization
• Access method

4
Types of File Organization

• Heap (unordered)
• Sequential (ordered or sorted)
• Hash (direct or random)
• Index

5
Heap

• Unordered structure
• Pros
• Simple
• No overhead
• Cons
• Slow
• Waste space (deletion)
• For
• Bulk-loaded
• Short file
• Retrieving 80 of the file

6
Ordered

• Sorted according to a field value or primary key
  field
• Pros
• Binary search
• Sequential processing
• Con
• Slow for retrieval information needed by
  management

7
Hash

• Terminology
• Hash field, hash key
• Collision, synonyms
• Bucket, slots
• Types
• Folding
• Division-remainder
• Collision handling
• Open addressing or unchained overflow
• Chained overflow
• Multiple hashing

8
Direct (Random or Hash)

• Pro
• Random processing
• Cons
• Sequential processing
• Updating (reorganization)

9
Indexes

• Terminology
• Primary index (one for each file)
• Secondary index for unique field or non-unique
  field (several for each file)
• Clustering index for clustering attribute
  (non-key field or non-unique field)
• Sparse index for some of the search key values
• Dense index for every search key value
• Types
• Linked list
• Inverted file
• Indexed sequential
• B-tree

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Indexed Sequential

• Structure
• Primary area
• Index area track no, highest key on the track,
  highest key in the overflow, address of first
  overflow record
• Overflow area address, record, pointer
• Types
• Indexed Sequential Access Method (ISAM)
• Virtual Sequential Access Method (VSAM)
• Pro
• Sequential random processing
• Con
• Waste spaces (deletion)
• Inefficient due to overflow

11
B-Tree

• Terminology
• Node
• Root
• Parent
• Child
• Leaf
• Depth
• Balanced tree
• Degree or order (n)
• Rules
• Root having two children
• Each node having n/2 and n pointers (children)
• Key values in leaf between (n-1)/2 and (n-1)
• Key values in non-leaf is 1 less than pointer
• Balanced tree
• Ordered values in leaf

12
Points to Remember

• Definition
• Types of Storage
• Types of File Organization

13
Assignment

• Review appendix c
• Read chapters 1 and 2 (skip relational calculus)
• Homework due date