Disk structure and access time in DBMS Theory - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to calculate the total access time for a disk operation.

DBMS Theory

total_access_time = seek_time + [1] + transfer_time

Drag options to blanks, or click blank then click option'

Arotational_latency

Bprocessing_delay

Cqueue_time

Dcache_hit_time

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing rotational latency with seek time.

Adding unrelated delays like cache hit time.

The total access time for a disk includes the seek time, rotational latency, and transfer time. Rotational latency is the delay waiting for the disk to rotate to the correct position.

2fill in blank

medium

Complete the formula to calculate average rotational latency given the disk's rotation speed in RPM.

DBMS Theory

average_rotational_latency = (60 / [1]) / 2

Drag options to blanks, or click blank then click option'

Atransfer_rate

Bseek_time

Crotation_speed_rpm

Dblock_size

Attempts:

3 left

💡 Hint

Common Mistakes

Using seek time instead of rotation speed.

Forgetting to divide by 2 for average latency.

The average rotational latency is half the time for one full rotation. The time for one rotation is 60 seconds divided by the rotation speed in RPM.

3fill in blank

hard

Fix the error in the code calculating transfer time for a disk block.

DBMS Theory

transfer_time = block_size / [1]

Drag options to blanks, or click blank then click option'

Arotational_latency

Brotation_speed_rpm

Cseek_time

Dtransfer_rate

Attempts:

3 left

💡 Hint

Common Mistakes

Using rotation speed or seek time instead of transfer rate.

Confusing units of measurement.

Transfer time is the time to read or write a block of data. It is calculated by dividing the block size by the transfer rate (data per second).

4fill in blank

hard

Fill in the blank to create a dictionary comprehension that maps block numbers to their access times if the access time is less than or equal to 10 ms.

DBMS Theory

{block: access_time for block, access_time in disk_access.items() if access_time [1] 10}

Drag options to blanks, or click blank then click option'

A<

B<=

C>=

D>

Attempts:

3 left

💡 Hint

Common Mistakes

Using greater than operators which select wrong blocks.

Mixing up the order of comparison operators.

The comprehension filters blocks with access times less than or equal to 10 milliseconds. Using <= ensures only blocks with access times less than or equal to 10 ms are included.

5fill in blank

hard

Fill all three blanks to create a dictionary comprehension that maps disk sectors to their sizes only if the sector size is greater than 512 bytes.

DBMS Theory

{ [1]: [2] for [3], size in sector_sizes.items() if size > 512 }

Drag options to blanks, or click blank then click option'

Asector

Bsize

Dblock

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect variable names for keys or values.

Not matching the variable names in the comprehension with the loop.

The comprehension maps each sector to its size, filtering only sectors with sizes greater than 512 bytes. The variable 'sector' is used as the key and 'size' as the value.