Appendix c
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Appendix C. File Organization & Storage Structure. Agenda. Definition Types of File Organization. Definition. Logical record & physical record File organization Access method. Types of File Organization. Heap (unordered) Sequential (ordered or sorted) Hash (direct or random) Index.

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Appendix C

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Appendix c

Appendix C

File Organization & Storage Structure


Agenda

Agenda

  • Definition

  • Types of File Organization


Definition

Definition

  • Logical record & physical record

  • File organization

  • Access method


Types of file organization

Types of File Organization

  • Heap (unordered)

  • Sequential (ordered or sorted)

  • Hash (direct or random)

  • Index


Appendix c

Heap

  • Unordered structure

  • Pros

    • Simple

    • No overhead

  • Cons

    • Slow

    • Waste space (deletion)

  • For

    • Bulk-loaded

    • Short file

    • Retrieving 80% of the file


Ordered

Ordered

  • Sorted according to a field value or primary key field

  • Pros

    • Binary search

    • Sequential processing

  • Con

    • Slow for retrieval information needed by management


Appendix c

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


Direct random or hash

Direct (Random or Hash)

  • Pro

    • Random processing

  • Cons

    • Sequential processing

    • Updating (reorganization)


Indexes

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


Indexed sequential

Indexed Sequential

  • Structure

    • Prime 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


B tree

B+-Tree

  • Terminology

    • Node

    • Root

    • Parent

    • Child

    • Leaf

    • Depth: the maximum number of level

    • Balanced tree

    • Degree or order (n): the maximum number of children

  • Rules

    • Root having at least two children

    • Each node having n/2 and n pointers (children)

    • Key values in leaf have to be between (n-1)/2 and (n-1)

    • Max no. of key values in non-leaf is 1 less than pointer

    • Balanced tree

    • Ordered values in leaf


Points to remember

Points to Remember

  • Definition

  • Types of File Organization


Assignment

Assignment

  • Review chapter 1 & appendix C

  • Read chapter 2

  • Group list due date: 9/18/07

  • Homework due date:


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