In Informix, which ALTER TABLE statement correctly changes the NEXT EXTENT SIZE for the customer table to 300 pages?

Introduction / Context:
This question focuses on Informix storage management, specifically how to modify the NEXT EXTENT SIZE of an existing table. Extents are contiguous units of disk space allocated to a table or index. Defining appropriate INITIAL and NEXT extent sizes can significantly affect performance and fragmentation behavior.

Given Data / Assumptions:

There is an existing table named customer.

The database is Informix or a compatible system that supports extent size clauses.

The goal is to change the NEXT EXTENT SIZE to 300 pages.

The change must be done using an ALTER TABLE statement.

Concept / Approach:
In Informix, NEXT SIZE determines how many pages are allocated when the table requires an additional extent. The MODIFY clause on ALTER TABLE is used to change storage parameters. The correct syntax uses MODIFY NEXT SIZE value, not MODIFY EXTENT SIZE or other variations. Therefore, we must identify the option that uses MODIFY NEXT SIZE with the correct numeric value.

Step-by-Step Solution:
1. Recall that to change the next extent allocation you use ALTER TABLE table_name MODIFY NEXT SIZE number. 2. Examine option A: ALTER TABLE customer MODIFY NEXT SIZE 300. This matches the expected syntax and sets the NEXT SIZE to 300 pages. 3. Option B uses MODIFY NEXT EXTENT SIZE, which is not the documented form of the clause. 4. Option C uses MODIFY EXTENT SIZE 300, which is ambiguous and does not match the specific NEXT SIZE keyword. 5. Option D omits the MODIFY keyword and does not follow the required ALTER TABLE syntax.

Verification / Alternative check:
The statement in option A can be tested in a development environment. If the ALTER TABLE executes successfully and system catalog views or oncheck output confirm the new NEXT EXTENT SIZE of 300 pages, then the syntax is validated.

Why Other Options Are Wrong:
Option B introduces an extra word EXTENT, which does not match the correct parameter name.
Option C alters a vague EXTENT SIZE and may not be accepted by the server, since NEXT SIZE is the intended parameter.
Option D omits MODIFY and therefore does not follow normal ALTER TABLE syntax in Informix.

Common Pitfalls:
A common mistake is confusing INITIAL SIZE and NEXT SIZE parameters. Another is assuming that a more descriptive phrase like NEXT EXTENT SIZE will be accepted when the engine expects a specific keyword. Always check exact syntax in the product documentation and avoid changing extent sizes in production without testing.

Final Answer:
The correct statement is ALTER TABLE customer MODIFY NEXT SIZE 300.