Exception Handling Definations

1. Introduction to PL/SQL Exceptions

1. Exceptions are runtime errors that disrupt normal execution flow.
2. They allow developers to detect, handle, and respond to errors.
3. PL/SQL provides structured mechanisms to manage exceptions.
4. Exception handling improves reliability and maintainability of programs.
5. Unhandled exceptions propagate to the calling environment, potentially aborting execution.

2. Types of Exceptions in Oracle

1. Predefined exceptions are supplied by Oracle.
2. User-defined exceptions are created by programmers.
3. System exceptions occur due to SQL engine errors.
4. Application exceptions occur due to program logic.
5. Each exception type is handled differently depending on context.

3. Predefined Exceptions

1. These are common runtime errors recognized by Oracle.
2. Examples include NO_DATA_FOUND, TOO_MANY_ROWS, ZERO_DIVIDE.
3. They automatically have associated exception names.
4. They do not need explicit declaration.
5. They can be directly handled using EXCEPTION blocks.

4. User-defined Exceptions

1. Created by the programmer for application-specific conditions.
2. Provide flexibility to handle custom error scenarios.
3. Can be raised explicitly using the RAISE statement.
4. Improve code readability and modularity.
5. Allow integration with business logic for error detection.

5. Declaring Exceptions

1. Exceptions must be declared in the declarative section of a block.
2. Both predefined and user-defined exceptions can be declared.
3. Declaration assigns a name to the exception.
4. Proper declaration ensures clear scope for exception handling.
5. Facilitates organized and maintainable error management.

6. Raising Exceptions

1. Exceptions can be raised automatically by Oracle for runtime errors.
2. User-defined exceptions are raised manually using RAISE.
3. Raising an exception interrupts normal execution flow.
4. Can be raised conditionally based on program logic.
5. Propagates control to the associated EXCEPTION block.

7. Handling Exceptions using EXCEPTION Block

1. The EXCEPTION block captures and manages errors.
2. Multiple exceptions can be handled within a single block.
3. Ensures graceful termination or continuation of program logic.
4. Provides structured error reporting and recovery mechanisms.
5. Avoids abrupt termination of PL/SQL blocks.

8. Propagating Exceptions

1. Exceptions not handled in the current block propagate to the caller.
2. Allows centralized error handling in higher-level programs.
3. Supports nested blocks and modular exception management.
4. Propagation ensures that critical errors are not ignored.
5. Can be controlled using RAISE in exception handling.

9. The WHEN OTHERS Clause

1. Catches all exceptions not explicitly handled.
2. Acts as a safety net for unforeseen errors.
3. Should generally be used as the last handler in an EXCEPTION block.
4. Useful for logging or cleanup operations.
5. Helps prevent unhandled exceptions from terminating the program.

10. Exception Hierarchy in PL/SQL

1. Predefined exceptions are part of a structured hierarchy.
2. User-defined exceptions can be integrated into the hierarchy.
3. Oracle checks exception handlers from top to bottom.
4. Handlers for specific exceptions take precedence over generic ones.
5. Understanding hierarchy ensures proper handling without conflicts.

11. Built-in Exception Codes

1. Each predefined exception has an associated error code.
2. Codes can be used to identify and diagnose errors programmatically.
3. Error codes assist in logging and debugging.
4. Enables differentiation of multiple errors of the same type.
5. Useful for automated exception reporting and recovery.

12. Using SQLCODE and SQLERRM

1. SQLCODE returns the numeric code of the last error.
2. SQLERRM returns the textual message of the last error.
3. Both provide detailed diagnostics within EXCEPTION blocks.
4. Useful for dynamic reporting and logging of errors.
5. Can be combined to understand the cause of failures.

13. Handling NO_DATA_FOUND Exception

1. Raised when a SELECT INTO query returns no rows.
2. Prevents program termination for missing data.
3. Allows default or alternate logic to execute.
4. Can be logged for auditing purposes.
5. Enhances program reliability for optional or empty datasets.

14. Handling TOO_MANY_ROWS Exception

1. Raised when a SELECT INTO query returns multiple rows.
2. Protects against unintentional data overwrites.
3. Allows the program to implement alternative handling logic.
4. Can trigger user notifications for ambiguous queries.
5. Helps maintain data integrity and control flow.

15. Handling ZERO_DIVIDE Exception

1. Raised when a division by zero occurs.
2. Prevents abrupt termination of mathematical operations.
3. Supports alternative computation logic.
4. Ensures program stability during invalid arithmetic operations.
5. Can be logged or reported for debugging purposes.

16. Handling INVALID_CURSOR Exception

1. Raised for invalid cursor operations (open, fetch, close).
2. Protects against cursor misuse or logical errors.
3. Ensures proper resource management in PL/SQL.
4. Helps maintain database performance and avoid leaks.
5. Enables controlled recovery from cursor-related errors.

17. Handling VALUE_ERROR Exception

1. Raised when conversion or assignment fails (e.g., numeric overflow).
2. Prevents unexpected runtime failures in data processing.
3. Enables validation and alternative logic for invalid inputs.
4. Supports safe conversion of data types.
5. Can be used to enforce program input constraints.

18. Handling DUP_VAL_ON_INDEX Exception

1. Raised when a unique constraint is violated.
2. Ensures data integrity at the database level.
3. Allows recovery or alternative insert/update logic.
4. Helps identify logical errors in application data handling.
5. Supports reporting and auditing for duplicate records.

19. Handling STORAGE_ERROR Exception

1. Raised when PL/SQL runs out of memory.
2. Helps prevent abrupt termination due to memory exhaustion.
3. Supports graceful error reporting and cleanup.
4. Allows application to attempt recovery or resource reallocation.
5. Critical for large data processing or resource-intensive operations.

20. Handling PROGRAM_ERROR Exception

1. Raised for internal PL/SQL runtime errors.
2. Signals issues in program logic or Oracle engine.
3. Can be used to capture unexpected failures for debugging.
4. Supports robust error management in complex programs.
5. Ensures controlled termination or logging of internal issues.

21. Handling LOGIN_DENIED Exception

1. Raised during invalid database connection attempts.
2. Helps secure application by detecting authentication failures.
3. Allows retry logic or alternative authentication flow.
4. Supports auditing of unauthorized access attempts.
5. Prevents abrupt application termination due to login errors.

22. Handling SELF-DEFINED Custom Exceptions

1. Created for application-specific error conditions.
2. Raises precise, meaningful errors for business logic.
3. Improves maintainability and readability of code.
4. Integrates with EXCEPTION blocks for controlled handling.
5. Supports proactive error detection and logging.

23. Using RAISE_APPLICATION_ERROR

1. Raises user-defined errors with custom codes and messages.
2. Allows propagation of errors from procedures or triggers.
3. Helps enforce application-specific validation rules.
4. Supports consistent error reporting across modules.
5. Can integrate with logging or alert mechanisms.

24. Exception Handling Best Practices

1. Handle only relevant exceptions explicitly.
2. Always include cleanup operations for resources.
3. Log or report errors for audit and debugging.
4. Avoid silent exception suppression except in controlled cases.
5. Maintain readability and modularity in exception handling.

25. Exception Handling in Procedures

1. Ensures procedures terminate gracefully on errors.
2. Allows propagation of exceptions to calling programs.
3. Facilitates logging and auditing inside procedures.
4. Enables custom recovery strategies for business logic.
5. Improves reliability and maintainability of procedures.

26. Exception Handling in Functions

1. Ensures functions return valid results even on errors.
2. Allows exception propagation to calling environments.
3. Supports consistent output for business logic.
4. Enables logging of function-specific errors.
5. Prevents disruption of dependent programs or packages.

27. Exception Handling in Triggers

1. Prevents database triggers from terminating unexpectedly.
2. Supports business rule enforcement with error handling.
3. Allows rollback or recovery of operations.
4. Provides auditing and logging of trigger exceptions.
5. Maintains database integrity and controlled operations.

28. Exception Handling in Packages

1. Centralizes exception handling for related procedures/functions.
2. Facilitates modular and reusable error management.
3. Enables consistent propagation strategies.
4. Supports logging and recovery for package-level operations.
5. Improves maintainability and readability of packaged logic.

29. Using PRAGMA EXCEPTION_INIT

1. Associates user-defined exceptions with specific Oracle error codes.
2. Facilitates handling of system errors with custom names.
3. Enhances readability and maintainability of code.
4. Allows precise control over exception behavior.
5. Integrates system and application-specific error handling.

30. Nested Exception Handling

1. Inner blocks can handle specific exceptions locally.
2. Outer blocks can handle propagated exceptions.
3. Provides multiple layers of error control.
4. Supports graceful recovery in complex programs.
5. Ensures modular and hierarchical exception management.

31. Propagation of Exceptions Across Blocks

1. Unhandled exceptions move to outer blocks.
2. Supports centralized error management.
3. Enables modular design with localized exception handling.
4. Maintains execution flow for nested and calling programs.
5. Ensures critical errors are properly escalated.

32. Logging Exceptions to a Table

1. Provides persistent storage for runtime errors.
2. Helps in debugging and auditing.
3. Supports automated monitoring and reporting.
4. Enables historical analysis of recurring errors.
5. Improves accountability and system reliability.

33. Debugging with Exceptions

1. Exception blocks provide detailed error diagnostics.
2. Use SQLCODE/SQLERRM for root cause analysis.
3. Helps identify logical or runtime issues.
4. Supports controlled testing of error scenarios.
5. Facilitates faster resolution of runtime problems.

34. Performance Considerations in Exception Handling

1. Excessive exception handling may add minor overhead.
2. Use targeted exception handling for efficiency.
3. Avoid unnecessary nested blocks for performance.
4. Logging should be optimized for high-volume programs.
5. Balance between robustness and performance is critical.

35. Handling Exceptions in Cursors

1. Cursor operations can raise exceptions like INVALID_CURSOR.
2. Exception handling ensures proper open, fetch, and close operations.
3. Prevents memory leaks and resource contention.
4. Supports recovery in case of cursor errors.
5. Enables controlled iteration and data processing.

36. Exception Handling with Transactions (COMMIT & ROLLBACK)

1. Exceptions can trigger ROLLBACK to maintain consistency.
2. COMMIT should only occur if no critical errors exist.
3. Supports atomic operations in business logic.
4. Ensures data integrity across multiple DML operations.
5. Facilitates error-driven transaction management.

37. Using SAVEPOINT for Exception Recovery

1. SAVEPOINT allows partial rollback within a transaction.
2. Enhances control during multiple-step operations.
3. Helps recover from specific errors without affecting entire transaction.
4. Supports modular and safe exception recovery strategies.
5. Maintains consistent state while handling runtime exceptions.

38. Exception Handling in Dynamic SQL

1. Dynamic SQL errors propagate to calling EXCEPTION blocks.
2. Requires careful handling due to runtime execution.
3. SQLCODE/SQLERRM helps diagnose dynamic execution issues.
4. Supports recovery from both DDL and DML runtime errors.
5. Integrates with logging and auditing for dynamic operations.

39. Global Exception Handling Strategies

1. Define centralized logging and error management routines.
2. Implement common handlers in packages for reuse.
3. Use WHEN OTHERS cautiously for global catch-all handling.
4. Ensure propagation and escalation are controlled.
5. Improve maintainability, monitoring, and system reliability.

40. Real-time Case Studies and Examples

1. Highlight critical runtime errors and recovery approaches.
2. Demonstrate exception propagation in nested programs.
3. Show best practices for logging and auditing exceptions.
4. Illustrate use of custom and predefined exceptions in enterprise apps.
5. Emphasize performance and reliability improvements through structured handling.