DIS Database Administration 3

Question 1

Which database isolation level prevents dirty reads but still allows non-repeatable reads?

Accepted Answer

Read Committed

Answer

Read Committed prevents dirty reads by only seeing committed data, but the same row can return different values if read twice within a transaction.

Question 2

A digital imaging system stores image vectors for similarity search. Which database extension or type is best suited for nearest-neighbor queries?

Accepted Answer

pgvector

Answer

pgvector is a PostgreSQL extension specifically designed for storing and querying high-dimensional vectors with similarity search operators.

Question 3

When designing a DIS database schema, a composite primary key on (session_id, image_sequence) is used. What potential issue arises for child tables referencing this key?

Accepted Answer

Foreign key constraints must reference all columns of the composite key

Answer

Foreign keys referencing a composite primary key must include all component columns in the same order.

Question 4

A DBA wants to enforce that every image record must have a non-null file_path. Which constraint type should be applied?

Accepted Answer

NOT NULL constraint

Answer

A NOT NULL constraint prevents the column from accepting null values, enforcing that every row must supply a file path.

Question 5

In a high-availability digital imaging database cluster, what is the purpose of a WAL (Write-Ahead Log)?

Accepted Answer

Ensuring changes are logged before being applied for crash recovery

Answer

WAL records every change before it is applied to data files, enabling the database to recover to a consistent state after a crash.

(DIS) Digital Imaging Specialist Certification Practice Test

(DIS) Digital Imaging Specialist Certification Practice Test

DIS Database Administration 3