What is bucket overflow and how bucket overflow is handled through Over Flow Chaining or Closed Hashing?

Ans: Bucket: unit of storage holding records. Bucket is a disk block or contiguous block .Bucket contains multiple records.

Hash Function: maps records to bucket numbers Function h from set of all search key values K to the set of all bucket addresses (numbers) B .Records along with different search key values may be mapped similar bucket. Whole bucket has to be searched to locate record. If bucket is full required overflow buckets and pointers

How to handle bucket overflow:

• Buckets overflow is handled through using overflow buckets
1. Closed Hashing (Chaining): The overflow buckets of a given bucket are chained together in a linked list
2. Open Hashing: place in further available bucket (not suitable for database applications)
3. Multiple Hashing : use a second hash function