An index is a physical structure containing pointers to the data.
32. What is extension and intension?
Extension -It is the number of tuples present in a table at any instance. This is time dependent.
Intension -It is a constant value that gives the name, structure of table and the constraints laid on it.
33. What do you mean by atomicity and aggregation?
Atomicity-Atomicity states that database modifications must follow an all or nothing rule. Each transaction is said to be atomic. If one part of the transaction fails, the entire transaction fails.
Aggregation – A feature of the entity relationship model that allows a relationship set to participate in another relationship set. This is indicated on an ER diagram by drawing a dashed box around the aggregation.
34. What is RDBMS KERNEL?
Two important pieces of RDBMS architecture are the kernel, which is the software, and the data dictionary, which consists of the system- level data structures used by the kernel to manage the database.
35. Name the sub-systems of a RDBMS?
I/O, Security, Language Processing, Process Control, Storage Management, Logging and Recovery, Distribution Control, Transaction Control, Memory Management, Lock Management.
36. How do you communicate with an RDBMS?
You communicate with an RDBMS using Structured Query Language (SQL)
37. Disadvantage in File Processing System?
· Data redundancy & inconsistency.
· Difficult in accessing data.
· Data isolation.
· Data integrity.
· Concurrent access is not possible.
· Security Problems.
38. What is VDL (View Definition Language)?
It specifies user views and their mappings to the conceptual schema.
39. What is SDL (Storage Definition Language)?
This language is to specify the internal schema. This language may Specify the mapping between two schemas.
40. Describe concurrency control?
Concurrency control is the process managing simultaneous operations against a database so that database integrity is no compromised. There are two approaches to concurrency control.
The pessimistic approach involves locking and the optimistic approach involves versioning.