Differentiate between static hashing and dynamic hashing, Database Management System

Differentiate between static hashing and dynamic hashing. 

Ans: Static Hashing comprises the number of primary pages in the directory fixed. So, while a bucket is full, we require an overflow bucket to store any extra records that hash to the full bucket. This can be completed with a link to an overflow page, or a linked list of overflow pages. The linked list can be separate for every bucket, or similar for all buckets that overflow. While searching for a record, the original bucket is accessed first, after that the overflow buckets. Specified there are several keys that hash to the same bucket, locating a record may need accessing multiple pages on disk that greatly degrades performance. 

The dilemma of lengthy searching of overflow buckets is solved by Dynamic Hashing. In Dynamic Hashing the size of the directory grows along with the number of collisions to accommodate new records and prevent long overflow page chains. Extendible and Linear Hashing are two dynamic hashing methods.

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