DB2 Performance Tuning

Code Example

## DB2 Performance Tuning

Optimize DB2 queries and applications for better performance.

### Query Optimization

**Use EXPLAIN:**
\`\`\`sql
EXPLAIN PLAN FOR SELECT ...
\`\`\`

**Access Paths:**
- Table scan (avoid for large tables)
- Index scan (preferred)
- Index-only access (best)

### Index Strategy

1. Create indexes on WHERE columns
2. Use composite indexes for multi-column WHERE
3. Put most selective column first
4. Avoid indexes on frequently updated columns

### SQL Best Practices

1. Be specific in SELECT (avoid SELECT *)
2. Use EXISTS instead of IN for subqueries
3. Avoid functions on indexed columns in WHERE
4. Use FETCH FIRST for limited results

### Cursor Optimization

- Use WITH HOLD only when needed
- Fetch multiple rows with ROWSET
- Close cursors promptly

### RUNSTATS
Keep statistics current for optimizer.