In an Informix database, which of the following is NOT typically considered an advantage of using fragmentation for tables and indexes?

Introduction / Context:
This question evaluates understanding of fragmentation in Informix or similar database systems. Fragmentation divides a table or index into multiple physical pieces based on rules such as round robin, expression based ranges or hashing. The main goal is to improve performance, manageability, and availability. The question specifically asks which listed item is not usually promoted as a key advantage.

Given Data / Assumptions:

The database engine supports fragmentation at the table or index level.

Fragments can be stored on different dbspaces and storage devices.

Parallel query, backup and restore operations can take advantage of fragments.

The options list potential characteristics or benefits of fragmenting objects.

Concept / Approach:
Well known benefits of fragmentation include increased availability, because some fragments can remain online even if others are down, improved performance by enabling parallel scans, and finer control over backup, restore and storage placement. However, fragmentation does not inherently reduce total disk space requirements. In some cases it can even increase metadata overhead or lead to wasted space if not designed carefully.

Step-by-Step Solution:
1. Recall the main documented benefits of fragmentation: performance through parallelism, improved manageability, and higher availability. 2. Examine option B, which states higher availability and better fault isolation. This aligns with the idea that a failure in one fragment may not affect others. 3. Examine option C, which points to finer granularity of archives and resources. Fragment level backup, restore and storage tuning are standard advantages. 4. Examine option D, which states that parallel scans are possible with PDQ across fragments, a core performance benefit. 5. Option A claims reduced disk space requirements, which is not a typical benefit and can even be the opposite in some designs, so it is the correct choice.

Verification / Alternative check:
Informix documentation and performance guides emphasise parallel query execution, flexibility of storage placement, and improved uptime as main reasons to fragment objects. They do not present fragmentation as a feature that directly reduces storage consumption.

Why Other Options Are Wrong:
Higher availability and better fault isolation are real advantages because fragments can be spread across devices or sites.
Finer granularity of archives and resources is an advantage because administrators can back up and manage subsets of data separately.
Parallel scans with PDQ are a major performance feature that relies on having multiple fragments to read concurrently.

Common Pitfalls:
Students sometimes assume that any advanced storage feature must save space. In reality, fragmentation is about distributing data and workload, not compressing it. Another pitfall is ignoring management overhead when increasing the number of fragments, which can offset some advantages if taken to an extreme.

Final Answer:
The option that is not typically considered an advantage of fragmentation is reduced disk space requirements.