Step 1: Understanding the Concept:
$\mathrm{S_N1}$ proceeds via a carbocation intermediate.
Step 2: Detailed Explanation:
In $\mathrm{S_N1}$ reactions, the carbocation intermediate is planar, leading to attack from both sides, resulting in both inversion and retention, hence racemization.
Step 3: Final Answer:
Racemization occurs due to both inversion and retention.