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Q: Explain predicate types
Answer:
Stage 1 predicates evaluated by storage engine. Stage 2 evaluated by DB2 (more expensive). Indexable predicates can use index. Non-indexable force scan. Design for stage 1/indexable predicates. EXPLAIN shows predicate staging.
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Q: How to tune DB2 queries?
Answer:
Check EXPLAIN output. Look at: access type (index vs scan), join method, sort operations. Add indexes for predicates. Rewrite with hints. Update statistics. Check for full tablespace scans. Monitor actual execution.
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Q: Explain access path selection
Answer:
Optimizer chooses access path based on statistics, predicates, indexes. Index scan vs tablespace scan. Join methods: nested loop, merge scan, hybrid. Sort operations. EXPLAIN reveals choice. Tuning influences path.