Periodicity of data: Are periodic data physically altered after insertion, or are they append-only and never updated once written?

Introduction / Context:Warehouse designers distinguish between transient (update-in-place) and periodic (append-only) data. Understanding this difference guides fact table strategy, auditing, and slowly changing dimensions.

Given Data / Assumptions:

• Periodic data captures history by adding new rows for changes.
• Once stored, prior records are preserved for time-based analysis.
• Updates occur by inserting a new version (and possibly closing the old one with an end date), not by altering the old row’s facts.

Concept / Approach:The essence of periodic data is immutability. For example, a daily inventory snapshot records stock levels each day; yesterday’s counts are not changed today. This supports accurate time-series analysis, trending, and auditing. Therefore, saying periodic data are “physically altered” contradicts the definition.

Step-by-Step Solution:

Verification / Alternative check:Inspect ETL for INSERT-only behavior on historical tables and for integrity checks ensuring that existing historical rows are not overwritten.

Why Other Options Are Wrong:

• Marking the statement “Correct” misdefines periodic data.
• Limiting the concept to specific schemas or platforms is unnecessary; periodicity is a modeling choice, not a technology constraint.

Common Pitfalls:Mixing transient updates into periodic stores, which corrupts history, or failing to manage end dates and overlapping effective periods, which breaks point-in-time reporting.

Final Answer:Incorrect