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Appendix C

Explore the various types of storage and file organization methods, from heap to B+-tree, with emphasis on access methods and indexes for efficient data retrieval.

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Appendix C

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  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 Storage • Primary • Secondary • Volatile • Non-volatile

  5. Types of File Organization • Heap • Sorted • Direct (random or hash) • Index

  6. Heap • Unordered structure • Pros • Simple • No overhead • Cons • Slow • Waste space (deletion) • For • Bulk-loaded • Short file • Retrieving 80% of the file • Having an indexed key field

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

  8. Direct (Random or Hash) • Terminology • Hash field, hash key • Collision, synonyms • Bucket, slots • Types • Folding • Division-remainder • Collision handling • Open addressing • Unchained overflow • Chained overflow • Multiple Hashing

  9. Direct (Random or Hash) • Pro • Random processing • Cons • Sequential processing • Updating (reorganization) • Secondary key retrieval

  10. Indexes • Terminology • Primary index (one for each file) • Secondary index for non-ordering field (several for each file) • Clustering index for clustering attribute (non-key field or not 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

  11. Indexed Sequential • Structure • Primary area • Index area: track no, highest key on track, highest key in overflow, address of first over flow 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

  12. 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

  13. Points to Remember • Definition • Types of Storage • Types of File Organization

  14. Assignment • Review chapters 1 & appendix c • Read chapters 2, 3 & 4 (skip relational calculus) • Turn in your group list on time (2/11/03)

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