Define Hash files organization

a. Hashing includes computing the address of a data item by calculating a function on the search key value. 

 b. A hash function h is a function from the set of all search key values K to the set of all bucket addresses B. 

 We select a number of buckets to correspond to the number of search key values we will comprise stored in the database. 

To carry out a lookup on a search key value K_i, we calculate hk_i, and search the bucket along with that address. 

 If two search keys i and j map to similar address, as h(Ki)=h(Kj), after that the bucket at the address acquired will consist of records with both search key values. 

 In this case we will have to verify the search key value of each record in the bucket to get the ones we want.