What is CICS FREE (APPC) command used for?

CICS FREE (APPC) is used to free APPC resources and deallocate APPC sessions, enabling proper cleanup of communication resources and memory in CICS environments.

What types of resources are freed by FREE (APPC)?

Resources freed include session resources (session cleanup, conversation termination), resource cleanup (memory deallocation, buffer cleanup, connection cleanup), error recovery (error cleanup, abnormal termination), and normal termination (completion cleanup, graceful termination).

How do I handle errors with CICS FREE (APPC)?

Always check the response code and implement appropriate error handling, including validation of free requests, proper handling of cleanup errors, and fallback procedures for failed cleanup operations.

What is the purpose of APPC resource deallocation?

APPC resource deallocation enables proper cleanup of communication resources, prevents resource leaks, manages memory efficiently, and ensures system stability by freeing allocated resources when they are no longer needed.

When should I use CICS FREE (APPC)?

Use this command when APPC communication is complete, when cleaning up after errors, when implementing proper resource management, or when ensuring system stability by freeing unused resources.

CICS FREE (APPC) - APPC Resource Deallocation

CICS FREE (APPC) frees APPC resources and deallocates APPC sessions. It enables programs to clean up APPC resources, manage session deallocation, and handle APPC resource cleanup in CICS environments.

What is CICS FREE (APPC)?

CICS FREE (APPC) is a command that allows programs to free APPC resources and deallocate APPC sessions. It provides resource cleanup capabilities, session deallocation, and resource management for CICS applications.

Command Syntax

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EXEC CICS FREE
    CONVID(conversation-id)
    [RESP(response-code)]
END-EXEC

Parameters

Required Parameters

CONVID(conversation-id) - Conversation ID of the APPC session to free

Optional Parameters

RESP(response-code) - Response code variable

Resource Deallocation Types

Session Deallocation

Freeing APPC session resources

• SESSION CLEANUP - Clean up session resources
• CONVERSATION TERMINATION - Terminate conversation
• RESOURCE RELEASE - Release allocated resources
• MEMORY CLEANUP - Clean up memory resources

Resource Cleanup

Cleaning up system resources

• MEMORY DEALLOCATION - Deallocate memory resources
• BUFFER CLEANUP - Clean up communication buffers
• CONNECTION CLEANUP - Clean up network connections
• STATE RESET - Reset conversation state

Error Recovery

Recovering from errors and cleaning up

• ERROR CLEANUP - Clean up after errors
• ABNORMAL TERMINATION - Handle abnormal termination
• RESOURCE RECOVERY - Recover from resource errors
• STATE RECOVERY - Recover conversation state

Normal Termination

Normal completion and cleanup

• COMPLETION CLEANUP - Clean up after completion
• GRACEFUL TERMINATION - Graceful session termination
• RESOURCE RETURN - Return resources to system
• STATUS UPDATE - Update system status

Programming Examples

Basic APPC Resource Deallocation

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       IDENTIFICATION DIVISION.
       PROGRAM-ID. FREE01.
       DATA DIVISION.
       WORKING-STORAGE SECTION.
       01  CONVERSATION-ID  PIC X(8) VALUE 'CONV001'.
       01  RESPONSE-CODE    PIC S9(8) COMP.
       
       PROCEDURE DIVISION.
           EXEC CICS FREE
               CONVID(CONVERSATION-ID)
               RESP(RESPONSE-CODE)
           END-EXEC
           
           IF RESPONSE-CODE = DFHRESP(NORMAL)
               DISPLAY 'APPC resources freed successfully'
               DISPLAY 'Conversation ID: ' CONVERSATION-ID
               DISPLAY 'Resources deallocated'
           ELSE
               DISPLAY 'Failed to free APPC resources'
           END-IF
           
           EXEC CICS RETURN END-EXEC.

Advanced Resource Cleanup

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       IDENTIFICATION DIVISION.
       PROGRAM-ID. FREE02.
       DATA DIVISION.
       WORKING-STORAGE SECTION.
       01  CONVERSATION-ID  PIC X(8) VALUE 'CONV002'.
       01  RESPONSE-CODE    PIC S9(8) COMP.
       01  CLEANUP-COUNT    PIC S9(2) COMP VALUE 0.
       01  MAX-CLEANUPS     PIC S9(2) COMP VALUE 3.
       
       PROCEDURE DIVISION.
           PERFORM CLEANUP-RESOURCES
           
           IF RESPONSE-CODE = DFHRESP(NORMAL)
               DISPLAY 'All resources cleaned up successfully'
               DISPLAY 'Cleanup count: ' CLEANUP-COUNT
           ELSE
               DISPLAY 'Resource cleanup failed'
           END-IF
           
           EXEC CICS RETURN END-EXEC.
       
       CLEANUP-RESOURCES.
           ADD 1 TO CLEANUP-COUNT
           
           EXEC CICS FREE
               CONVID(CONVERSATION-ID)
               RESP(RESPONSE-CODE)
           END-EXEC
           
           IF RESPONSE-CODE = DFHRESP(NORMAL)
               DISPLAY 'Cleanup ' CLEANUP-COUNT ' successful'
           ELSE
               DISPLAY 'Cleanup ' CLEANUP-COUNT ' failed'
           END-IF.

Error Handling with Resource Deallocation

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       IDENTIFICATION DIVISION.
       PROGRAM-ID. FREE03.
       DATA DIVISION.
       WORKING-STORAGE SECTION.
       01  CONVERSATION-ID  PIC X(8) VALUE 'CONV003'.
       01  RESPONSE-CODE    PIC S9(8) COMP.
       
       PROCEDURE DIVISION.
           EXEC CICS FREE
               CONVID(CONVERSATION-ID)
               RESP(RESPONSE-CODE)
           END-EXEC
           
           EVALUATE RESPONSE-CODE
               WHEN DFHRESP(NORMAL)
                   DISPLAY 'APPC resources freed successfully'
               WHEN DFHRESP(NOTFND)
                   DISPLAY 'Conversation not found'
               WHEN DFHRESP(INVREQ)
                   DISPLAY 'Invalid free request'
               WHEN DFHRESP(APPCERR)
                   DISPLAY 'APPC-specific error occurred'
               WHEN DFHRESP(RESOURCEERR)
                   DISPLAY 'Resource-specific error occurred'
               WHEN OTHER
                   DISPLAY 'Unexpected error occurred'
           END-EVALUATE
           
           EXEC CICS RETURN END-EXEC.

Resource Management

Resource Deallocation

• Session Resources - Deallocate session resources
• Memory Resources - Free memory allocations
• Network Resources - Clean up network resources
• System Resources - Return system resources

Cleanup Procedures

• Resource Validation - Validate resource state before cleanup
• Cleanup Execution - Execute cleanup procedures
• Resource Verification - Verify cleanup completion
• Status Update - Update system status

Error Recovery

• Error Detection - Detect cleanup errors
• Error Recovery - Recover from cleanup errors
• Error Reporting - Report cleanup errors
• Error Prevention - Prevent cleanup errors

Resource Monitoring

• Resource Tracking - Track resource usage
• Resource Monitoring - Monitor resource state
• Resource Optimization - Optimize resource usage
• Resource Reporting - Report resource status

Error Handling

Common Response Codes

DFHRESP(NORMAL) - APPC resources freed successfully
DFHRESP(NOTFND) - Conversation not found
DFHRESP(INVREQ) - Invalid free request
DFHRESP(APPCERR) - APPC-specific error
DFHRESP(RESOURCEERR) - Resource-specific error
DFHRESP(NOTAUTH) - Not authorized to free resources

Performance Considerations

Cleanup Efficiency

• Optimize cleanup patterns - Use appropriate cleanup patterns for different scenarios
• Minimize cleanup overhead - Reduce the computational cost of cleanup
• Use efficient cleanup strategies - Implement cleanup strategies that minimize resource usage
• Monitor cleanup performance - Track the performance impact of cleanup

Resource Impact

• Monitor resource usage - Track how cleanup affects system resources
• Optimize resource allocation - Ensure efficient allocation of resources for cleanup
• Manage resource cleanup - Properly clean up resources after operations
• Track resource utilization - Monitor the overall resource consumption patterns

Best Practices

APPC Resource Deallocation Best Practices

• Always check response codes
• Use appropriate cleanup parameters
• Implement proper error handling
• Ensure proper resource management
• Validate cleanup operations
• Optimize cleanup operations
• Clean up resources promptly

Explain It Like I'm 5 Years Old

Think of CICS FREE (APPC) like cleaning up after playing:

• Put Toys Away: "Put all your toys back in the toy box" - Free resources
• Clean Up Room: "Clean up your room" - Clean up session
• Turn Off Lights: "Turn off the lights when you leave" - Close connections
• Close Door: "Close the door behind you" - End conversation
• All Done: "Everything is clean and tidy" - Resources freed

Exercises

Exercise 1: Basic Resource Deallocation

Create a program that allocates APPC resources and then frees them properly.

Exercise 2: Comprehensive Cleanup

Write a program that performs comprehensive resource cleanup with proper error handling.

Exercise 3: Error Handling

Implement comprehensive error handling for resource deallocation failures.

CICS FREE (APPC) - APPC Resource Deallocation

What is CICS FREE (APPC)?

Command Syntax

Parameters

Required Parameters

Optional Parameters

Resource Deallocation Types

Session Deallocation

Resource Cleanup

Error Recovery

Normal Termination

Programming Examples

Basic APPC Resource Deallocation

Advanced Resource Cleanup

Error Handling with Resource Deallocation

Resource Management

Resource Deallocation

Cleanup Procedures

Error Recovery

Resource Monitoring

Error Handling

Common Response Codes

Performance Considerations

Cleanup Efficiency

Resource Impact

Best Practices

APPC Resource Deallocation Best Practices

Explain It Like I'm 5 Years Old

Exercises

Exercise 1: Basic Resource Deallocation

Exercise 2: Comprehensive Cleanup

Exercise 3: Error Handling

Related Concepts

APPC Communication

Resource Management

Session Management

Memory Management

Error Handling

Related Pages