The answer is a k value set too low, which causes the nearest neighbor search to return no results. In vector databases like OCI OpenSearch used for retrieval-augmented generation, the k parameter defines the number of top candidate vectors to retrieve from the index. When k is too small, the search algorithm may not reach any relevant documents within that narrow candidate pool, especially if the query vector lies far from the indexed vectors in the embedding space. On the Oracle Cloud Infrastructure Generative AI Professional 1Z0-1127 exam, this concept tests your understanding of approximate nearest neighbor search tuning and the trade-off between recall and latency. A common trap is confusing k with the final number of results returned—k only controls the candidate pool size, not the final count. Remember the mnemonic: "Small k, no luck—raise the k to unlock."
1Z0-1127 Practice Question: Building LLM Applications with RAG and Vector Search
This 1Z0-1127 practice question tests your understanding of building llm applications with rag and vector search. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A team uses OCI OpenSearch as a vector database for RAG. Some queries return no results despite relevant documents being indexed. What is a likely cause?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The number of candidates (k) is set too low
If k (the number of nearest neighbors to return) is set too low, the search may not find any documents within the top k, returning no results.
Key principle: OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
The vector index is not refreshed after adding documents
Why it's wrong here
If the index is not refreshed, newly added documents are not searchable; but this would affect all queries, not just some.
✓
The number of candidates (k) is set too low
Why this is correct
A very low k value may result in no matches being returned for queries with distant nearest neighbors.
The query text is too long for the embedding model
Why it's wrong here
Most embedding models truncate long text, but this would still produce an embedding and return some results.
✗
The embedding model is incompatible with the document language
Why it's wrong here
Incompatibility might cause poor retrieval, but not necessarily zero results.
Common exam traps
Common exam trap: OSPF can fail even when IP connectivity looks correct
OSPF neighbour formation depends on matching areas, timers, network type, authentication and passive-interface behaviour. Do not choose an answer only because the devices can ping.
Detailed technical explanation
How to think about this question
OSPF questions usually test the details that control adjacency and route selection. Read the neighbour state, area, router ID and interface configuration before deciding what is wrong.
KKey Concepts to Remember
OSPF neighbours must agree on key parameters.
Router ID selection can affect neighbour relationships and LSDB output.
OSPF cost influences the preferred path.
A route can appear in OSPF information but not become the installed route.
TExam Day Tips
→Check area mismatch first when OSPF adjacency fails.
→Review passive interfaces when a network is advertised but no neighbour forms.
→Use show ip ospf neighbor and show ip route clues carefully.
Key takeaway
OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.
Real-world example
How this comes up in practice
A network engineer at a university connects two campus buildings via a fibre link. Both routers run OSPF, but no adjacency forms — even though both routers can ping each other. The engineer finds one router is in area 0 and the other in area 1. OSPF adjacency requires matching area numbers, hello/dead timers, and network type. IP reachability alone is not enough.
What to study next
Got this wrong? Here's your next step.
Review OSPF neighbour requirements — matching area type, hello and dead timers, network type, stub flags, and authentication. Study show ip ospf neighbor states (INIT, 2-WAY, FULL). Then practise related 1Z0-1127 OSPF questions on adjacency and route selection.
Building LLM Applications with RAG and Vector Search — This question tests Building LLM Applications with RAG and Vector Search — OSPF neighbours must agree on key parameters..
What is the correct answer to this question?
The correct answer is: The number of candidates (k) is set too low — If k (the number of nearest neighbors to return) is set too low, the search may not find any documents within the top k, returning no results.
What should I do if I get this 1Z0-1127 question wrong?
Review OSPF neighbour requirements — matching area type, hello and dead timers, network type, stub flags, and authentication. Study show ip ospf neighbor states (INIT, 2-WAY, FULL). Then practise related 1Z0-1127 OSPF questions on adjacency and route selection.
What is the key concept behind this question?
OSPF neighbours must agree on key parameters.
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