Capability milestones in distributed DBMS evolution Which of the following is NOT commonly listed as a stage in the historical evolution of distributed DBMS capability?

Introduction / Context:
Distributed DBMS capability evolved from simple remote access to fully distributed queries and transactions. Terminology varies slightly across sources, but typical stages include remote request, remote unit of work, distributed unit of work, and distributed request. Recognizing the odd one out requires recalling these standard milestones.

Given Data / Assumptions:

• We consider progression in terms of how much of a statement/transaction can span sites.
• “Remote” implies operations at one nonlocal site at a time.
• “Distributed” implies multiple sites within one unit of work.

Concept / Approach:

Common taxonomy: (1) Remote request (single SQL statement sent to a remote site), (2) Remote unit of work (multiple statements, but at one remote site per unit of work), (3) Distributed unit of work (a transaction spans multiple sites, one site per statement), (4) Distributed request (a single SQL statement can access data at multiple sites). “Unit of work” by itself, without the “remote” qualifier, refers to a local capability that predates distributed features and is not part of the distributed milestone list.

Step-by-Step Solution:

Verification / Alternative check:

Reference texts and vendor docs (e.g., early IBM/ISO terminology) follow the above naming. While terms can vary, the unqualified “unit of work” is generally not counted among distributed milestones.

Why Other Options Are Wrong:

• Remote unit of work: recognized stage.
• Distributed unit of work: recognized stage.
• Distributed request: recognized stage.
• Remote request: recognized stage.

Common Pitfalls:

• Confusing “unit of work” (transaction scope) with distributed capability categories.

Final Answer:

Unit of work (without remote capability).