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Q: How to create image copy?
Answer:
COPY utility creates backup. COPY TABLESPACE db.ts. FULL or INCREMENTAL. SHRLEVEL REFERENCE or CHANGE. Store in GDG for versions. Regular copies essential for recovery. COPYTOCOPY duplicates copies.
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Q: How to handle file status 22?
Answer:
Status 22 is duplicate key on WRITE or REWRITE attempt. KSDS primary key must be unique. Check program logic. May indicate data error. Use DUPLICATES option on AIX only if needed.
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Q: Explain NONUNIQUEKEY?
Answer:
AIX can have NONUNIQUEKEY (duplicates). Base cluster KSDS always unique primary key. NONUNIQUEKEY AIX returns first match, use READ NEXT for others. UNIQUEKEY if one-to-one.
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Q: How to use UNION?
Answer:
UNION combines SELECT results. UNION removes duplicates, UNION ALL keeps all. Column count and types must match. ORDER BY at end only. UNION expensive due to sort. Use UNION ALL if duplicates OK or impossible.
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Q: Explain CREATE INDEX
Answer:
CREATE INDEX creates index on table. CREATE INDEX idx ON table(col1, col2). UNIQUE prevents duplicates. CLUSTER determines physical order. Include columns for index-only access. Drop unused indexes for insert performance.
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Q: Explain ALTERNATE RECORD KEY
Answer:
ALTERNATE RECORD KEY defines secondary indexes for INDEXED files. SELECT file-name ALTERNATE RECORD KEY IS ALT-KEY WITH DUPLICATES. Allows access by multiple keys. DUPLICATES permits non-unique values. Define path in VSAM cluster.
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Q: What is REPLICATE option?
Answer:
REPLICATE duplicates sequence set on each track. Each track has own copy of sequence set index. Reduces contention. Obsolete with modern systems. Uses more space.