Comments on ISAM
File creation: Leaf (data) pages allocated sequentially, sorted by search key; then index pages allocated, then space for overflow pages.
Index entries: <search key value, page id> they `directí search for data entries, which are in leaf pages.
Search: Start at root; use key comparisons to go to leaf. Cost log F N ; F = # entries/index pg, N = # leaf pgs
Insert: Find leaf data entry belongs to, and put it there.
Delete: Find and remove from leaf; if empty overflow page, de-allocate.
- Static tree structure: inserts/deletes affect only leaf pages.