Oracle Database 19c: SQL Tuning Workshop — Lesson 2: Execution Plans, Cardinality, Join Methods, Access Paths, and Runtime

Learning Objectives

• Explain the architecture, workflow, or business purpose behind DBMS_XPLAN formats, predicates, estimates, and actual rows.
• Apply cardinality errors, selectivity, histograms, and correlation and nested loops, hash joins, merge joins, and join order in a controlled scenario.
• Validate outcomes and troubleshoot risks involving full scans, index access, partition pruning, row sources, and SQL Monitor awareness.

Detailed Topics

• DBMS_XPLAN formats, predicates, estimates, and actual rows
• cardinality errors, selectivity, histograms, and correlation
• nested loops, hash joins, merge joins, and join order
• full scans, index access, partition pruning, row sources, and SQL Monitor awareness

Instructor Demonstration

Demonstrate DBMS_XPLAN formats, predicates, estimates, and actual rows within a reporting query and transaction query tuned without sacrificing correctness, concurrency, or plan stability, then capture the exact configuration, command, transaction, report, model, query, code, or process evidence that proves the result for lesson 2.

Hands-On Exercise

Implement a controlled exercise covering cardinality errors, selectivity, histograms, and correlation and nested loops, hash joins, merge joins, and join order, then introduce and resolve an exception involving full scans, index access, partition pruning, row sources, and SQL Monitor awareness while preserving before-and-after evidence.

1. Confirm the environment, identities, inputs, dependencies, risks, and expected outcome.
2. Complete the course-specific configuration, development, analysis, or process workflow.
3. Capture settings, commands, data, outputs, logs, reports, screenshots, calculations, or test results.
4. Compare the observed result with acceptance criteria and document corrective action.

Scenario Analysis

• Identify the technical or business decision that must be made.
• Compare valid approaches and their security, performance, reliability, cost, compliance, and support trade-offs.
• Define rollback, recovery, ownership, communication, and evidence requirements.

Troubleshooting Guidance

Diagnose issues across DBMS_XPLAN formats, predicates, estimates, and actual rows, cardinality errors, selectivity, histograms, and correlation, nested loops, hash joins, merge joins, and join order, full scans, index access, partition pruning, row sources, and SQL Monitor awareness without making an unverified production change. Separate symptoms from causes, gather evidence, test the smallest reversible correction, rerun validation, and record preventive action.

Validation Checklist

• The requirement, scope, inputs, dependencies, and expected result are documented.
• The result is reproducible and supported by course-specific evidence.
• Normal, boundary, failure, security, performance, and operational conditions are reviewed.
• Exceptions, rollback, ownership, and the next improvement priority are recorded.

Lesson Outcome

Learners can apply Execution Plans, Cardinality, Join Methods, Access Paths, and Runtime in a realistic Oracle Database 19c: SQL Tuning Workshop scenario and validate the result with documented evidence.