Appendix C File Organization & Storage Structure

Agenda Definition Types of Storage Types of File Organization

Definition Logical record & physical record File organization Access method

Types of Storage Primary Secondary Volatile Non-volatile

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

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

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

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

Direct (Random or Hash) Pro –Random processing Cons –Sequential processing –Updating (reorganization) –Secondary key retrieval

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

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

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

Points to Remember Definition Types of Storage Types of File Organization

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