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Q: Explain UNIQUE vs SUBALLOCATION
Answer:
UNIQUE cluster gets own VSAM dataspace. SUBALLOCATION shares space with others. SUBALLOCATION deprecated, use UNIQUE. Modern systems prefer UNIQUE for isolation.
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Q: What causes -911 SQLCODE?
Answer:
-911 is deadlock or timeout. Two processes waiting for each other's resources. Solutions: consistent lock order, shorter transactions, COMMIT frequently, appropriate isolation level. -913 is similar (deadlock victim). Retry transaction.
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Q: Explain DB2 isolation levels
Answer:
UR (Uncommitted Read) reads dirty data. CS (Cursor Stability) locks current row. RS (Read Stability) locks all accessed rows. RR (Repeatable Read) locks range, prevents phantom. Higher isolation = more consistency but more locking. CS most common.
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Q: What is BIND command?
Answer:
BIND creates plan/package from DBRM. BIND PLAN(name) MEMBER(dbrm). Options: ISOLATION, VALIDATE, EXPLAIN. REBIND updates existing. BIND PACKAGE for packages. Precompile creates DBRM, BIND makes executable.
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Q: What is FETCH SENSITIVE cursor?
Answer:
SENSITIVE cursor reflects concurrent changes by other processes. EXEC SQL DECLARE cursor SENSITIVE STATIC/DYNAMIC SCROLL CURSOR. INSENSITIVE does not see changes. Affects isolation behavior. Consider performance impact.