Memory Hierarchy: Cost vs Access Time

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Questions and Answers

Which of the following statements accurately describes the memory hierarchy in terms of cost and access time?

Cache memory is more expensive and has a faster access time than main memory. (correct)
Registers are the least expensive and have the slowest access time.
Hard disk drives are more expensive and have a faster access time than cache memory.
Tertiary Storage is the most expensive and has the fastest access time.

What is the primary purpose of partitioning a database file into fixed-length blocks?

To optimize the transfer of data to and from storage. (correct)
To reduce the overall storage size of the database.
To enable variable-length records within the file.
To allow different databases to use the same file.

Within a database block, what is the role of the 'Table directory'?

To store the actual row data contained in the block.
To maintain information about the rows (IDs, addresses) within the block.
To list the tables that have rows stored in the block. (correct)
To provide general information such as block address and segment type.

Why is it generally recommended to store records of different relations in separate files?

To minimize disk accesses when retrieving related records. (C) Signup and view all the answers

What is a key advantage of using fixed-length records in file organization?

Simplified implementation and easier access. (A) Signup and view all the answers

In the context of file organization, what is the primary purpose of using 'end-of-record' symbols or storing record lengths?

To know when a record ends, especially in variable-length records. (B) Signup and view all the answers

Considering the trade-offs in deleting a record, what is a potential disadvantage of marking a record as deleted (tombstone approach)?

Increased complexity in record retrieval due to the need to skip tombstoned records. (C) Signup and view all the answers

In a slotted page structure, how is space utilization optimized when records are moved?

By compacting records to the beginning of the block, reducing fragmentation. (D) Signup and view all the answers

What is the key characteristic of an 'unspanned' record organization in file storage?

Records fill blocks and do not cross block boundaries, ensuring completeness within a block. (B) Signup and view all the answers

In database systems, what are Binary Large Objects (BLOBs) primarily used for?

Storing large, unstructured data such as images and audio. (D) Signup and view all the answers

What is a primary advantage of organizing a table in a row-wise manner (row-store)?

Suitable for Online Transaction Processing (OLTP) with efficient access to complete records. (D) Signup and view all the answers

What is a primary assumption that makes storing column values sequentially (column-store) an efficient strategy?

Frequent access to only specific columns for aggregations or analytical processing. (A) Signup and view all the answers

In a column-oriented database, what is a significant challenge compared to row-oriented databases?

Reconstructing a whole record when most parts of a record are needed. (C) Signup and view all the answers

For what type of workload are column stores most suitable?

Read-mostly, read-intensive, large data repositories. (D) Signup and view all the answers

What is a key advantage of column stores over row stores in the context of analytical queries?

Improved I/O efficiency by fetching only required columns. (D) Signup and view all the answers

What is the purpose of indexing in database management systems?

To speed up the retrieval of data. (C) Signup and view all the answers

What is the primary difference between a primary index and a secondary index?

Primary indexes physically reorder the data, while secondary indexes do not. (B) Signup and view all the answers

Which of the following search methods is typically associated with primary indexes to enable efficient data retrieval?

Skip-forward search (B) Signup and view all the answers

What is a key benefit of using secondary indexes in a database?

Speeding up joins on foreign key constraints. (A) Signup and view all the answers

How does a 'dense' index differ from a 'sparse' index?

Dense indexes contain an entry for every record, while sparse indexes contain entries for blocks of records. (D) Signup and view all the answers

What is the primary implication of creating multiple secondary indexes on a table?

Increased storage space and potential impact on update performance. (B) Signup and view all the answers

If a column is defined with a `UNIQUE` constraint, what is a typical database system behavior regarding indexes?

The system automatically creates an index on that column by default. (C) Signup and view all the answers

What is the main advantage that Primary and Clustering indexes have over Secondary indexes?

Can use block anchors. (E) Signup and view all the answers

In the context of database file organization, what does the term "fragmentation" refer to?

The allocation of non-contiguous memory space to a single file, resulting in slower access times. (D) Signup and view all the answers

What is a major factor that determines which indexes to create for a database?

The physical database tuning. (D) Signup and view all the answers

In the context of file storage, what is the 'buffer pool'?

An allocation of contiguous pages for large objects. (C) Signup and view all the answers

How can a database be configured to improve performance with aggregate queries?

Column storage (C) Signup and view all the answers

What is the function block address?

Header contains general block information (A) Signup and view all the answers

What is true about database blocks? (pages & blocks may be used interchangeably in books)

Contains Overhead and Payload (D) Signup and view all the answers

How can file records be structured?

Both are valid (D) Signup and view all the answers

What's the purpose of "Slotted page structure?"

To move records to use up space and have no fragmentation (D) Signup and view all the answers

What is true about Row-stores?

All of the above (D) Signup and view all the answers

What is true about Column stores?

All of the above (D) Signup and view all the answers

What is TPC-H intended for?

Decision Support, i.e., OLAP (OnLine Analytical Processing) (A) Signup and view all the answers

What does the SQL command `CREATE UNIQUE INDEX` do?

Creates a unique index in the table. (B) Signup and view all the answers

Why shouldn't you always index everything?

All of the above (D) Signup and view all the answers

Which of the following elements are part of a block?

All of the above (E) Signup and view all the answers

Which index types can use block anchors?

A and B (D) Signup and view all the answers

In what order is the block organized?

Common and Variable Header, Table Directory, Row Directory, Free Space, Row Data (B) Signup and view all the answers

Flashcards

What are files in databases?

Databases are mapped into a number of these for persistent storage.

What are blocks?

Each file is divided into these fixed-length units.