Step 3: Ask These Questions

Review the execution plan and look for red flags:

Question	What to Look For
Are there full table scans?	Look for TABLE ACCESS FULL on large tables
Are joins using hash or nested loops?	Hash joins are usually good for large inputs. Nested loops on big tables may be slow.
Are estimated rows way off from actual rows?	That means bad stats or data skew.
Is there temp usage?	Indicates a sort, hash join, or aggregation that didn’t fit in memory.
Is the plan parallel?	Look for PX steps. If it’s not using parallel and it should, the query may be underutilizing the ADW architecture.