Progress0 of 0 lessons

CICS FREE - Resource Deallocation

CICS FREE provides resource deallocation capabilities for programs and transactions. It enables programs to free resources, manage resource cleanup, and handle resource deallocation in CICS environments.

What is CICS FREE?

CICS FREE is a command that allows programs to deallocate resources in the system. It provides resource deallocation capabilities, resource cleanup, and resource management for CICS applications.

Command Syntax

cobol
1
2
3
4
EXEC CICS FREE
    RESOURCE(resource-name)
    [RESP(response-code)]
END-EXEC

Parameters

Required Parameters

  • RESOURCE(resource-name) - Name of resource to free

Optional Parameters

  • RESP(response-code) - Response code variable

Resource Types

Memory Resources

Memory resource types

  • • MAIN STORAGE - Main storage resources
  • • AUXILIARY STORAGE - Auxiliary storage resources
  • • VIRTUAL STORAGE - Virtual storage resources
  • • SHARED STORAGE - Shared storage resources

File Resources

File resource types

  • • VSAM FILES - VSAM file resources
  • • QSAM FILES - QSAM file resources
  • • BDAM FILES - BDAM file resources
  • • ISAM FILES - ISAM file resources

Communication Resources

Communication resource types

  • • CONVERSATIONS - Conversation resources
  • • SESSIONS - Session resources
  • • CONNECTIONS - Connection resources
  • • CHANNELS - Channel resources

System Resources

System resource types

  • • PROCESSES - Process resources
  • • THREADS - Thread resources
  • • LOCKS - Lock resources
  • • EVENTS - Event resources

Programming Examples

Basic Resource Deallocation

cobol
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
       IDENTIFICATION DIVISION.
       PROGRAM-ID. FREE01.
       DATA DIVISION.
       WORKING-STORAGE SECTION.
       01  RESOURCE-NAME PIC X(8) VALUE 'MAINMEM'.
       01  RESPONSE-CODE PIC S9(8) COMP.
       
       PROCEDURE DIVISION.
           DISPLAY 'Freeing resource'
           DISPLAY 'Resource: ' RESOURCE-NAME
           
           EXEC CICS FREE
               RESOURCE(RESOURCE-NAME)
               RESP(RESPONSE-CODE)
           END-EXEC
           
           IF RESPONSE-CODE = DFHRESP(NORMAL)
               DISPLAY 'Resource freed successfully'
           ELSE
               DISPLAY 'Resource free failed'
           END-IF
           
           EXEC CICS RETURN END-EXEC.

Advanced Resource Management

cobol
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
       IDENTIFICATION DIVISION.
       PROGRAM-ID. FREE02.
       DATA DIVISION.
       WORKING-STORAGE SECTION.
       01  RESOURCE-NAME PIC X(8).
       01  RESPONSE-CODE PIC S9(8) COMP.
       01  FREE-COUNT PIC S9(2) COMP VALUE 0.
       01  MAX-FREES PIC S9(2) COMP VALUE 3.
       01  RESOURCE-LIST.
           05  RESOURCE-ITEM OCCURS 3 TIMES.
               10  RESOURCE-ID PIC X(8).
               10  RESOURCE-STATUS PIC X(1).
       
       PROCEDURE DIVISION.
           PERFORM INITIALIZE-RESOURCES
           PERFORM FREE-MULTIPLE-RESOURCES
           
           EXEC CICS RETURN END-EXEC.
       
       INITIALIZE-RESOURCES.
           MOVE 'MAINMEM' TO RESOURCE-ID(1)
           MOVE 'VSAMFILE' TO RESOURCE-ID(2)
           MOVE 'CONVERS' TO RESOURCE-ID(3).
       
       FREE-MULTIPLE-RESOURCES.
           PERFORM VARYING FREE-COUNT FROM 1 BY 1
               UNTIL FREE-COUNT > MAX-FREES
               
               MOVE RESOURCE-ID(FREE-COUNT) TO RESOURCE-NAME
               PERFORM FREE-SINGLE-RESOURCE
               
               IF RESPONSE-CODE = DFHRESP(NORMAL)
                   MOVE 'F' TO RESOURCE-STATUS(FREE-COUNT)
                   DISPLAY 'Resource ' FREE-COUNT ' freed successfully'
               ELSE
                   MOVE 'E' TO RESOURCE-STATUS(FREE-COUNT)
                   DISPLAY 'Resource ' FREE-COUNT ' free failed'
               END-IF
           END-PERFORM.
       
       FREE-SINGLE-RESOURCE.
           EXEC CICS FREE
               RESOURCE(RESOURCE-NAME)
               RESP(RESPONSE-CODE)
           END-EXEC.

Error Handling with Resource Deallocation

cobol
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
       IDENTIFICATION DIVISION.
       PROGRAM-ID. FREE03.
       DATA DIVISION.
       WORKING-STORAGE SECTION.
       01  RESOURCE-NAME PIC X(8) VALUE 'MAINMEM'.
       01  RESPONSE-CODE PIC S9(8) COMP.
       01  RETRY-COUNT PIC S9(2) COMP VALUE 0.
       01  MAX-RETRIES PIC S9(2) COMP VALUE 3.
       01  FREE-SUCCESSFUL PIC X(1) VALUE 'N'.
       
       PROCEDURE DIVISION.
           PERFORM FREE-RESOURCE-WITH-RETRY
           
           EXEC CICS RETURN END-EXEC.
       
       FREE-RESOURCE-WITH-RETRY.
           PERFORM FREE-RESOURCE
           
           IF RESPONSE-CODE NOT = DFHRESP(NORMAL)
               AND RETRY-COUNT < MAX-RETRIES
               ADD 1 TO RETRY-COUNT
               DISPLAY 'Retry ' RETRY-COUNT ' resource free operation'
               PERFORM FREE-RESOURCE-WITH-RETRY
           END-IF.
       
       FREE-RESOURCE.
           EXEC CICS FREE
               RESOURCE(RESOURCE-NAME)
               RESP(RESPONSE-CODE)
           END-EXEC
           
           EVALUATE RESPONSE-CODE
               WHEN DFHRESP(NORMAL)
                   MOVE 'Y' TO FREE-SUCCESSFUL
                   DISPLAY 'Resource free operation successful'
               WHEN DFHRESP(NOTAUTH)
                   DISPLAY 'Not authorized to free resource'
               WHEN DFHRESP(INVREQ)
                   DISPLAY 'Invalid resource free request'
               WHEN DFHRESP(RESOURCEERR)
                   DISPLAY 'Resource free operation error'
               WHEN DFHRESP(RESOURCENOTFOUND)
                   DISPLAY 'Resource not found'
               WHEN DFHRESP(RESOURCEINUSE)
                   DISPLAY 'Resource is in use'
               WHEN OTHER
                   DISPLAY 'Unexpected resource free error'
           END-EVALUATE.

Resource Management

Resource Deallocation

  • • Resource Free - Free allocated resources
  • • Resource Cleanup - Clean up resource state
  • • Resource Validation - Validate resource state
  • • Resource Monitoring - Monitor resource status

Resource Lifecycle

  • • Resource Allocation - Allocate resources
  • • Resource Usage - Use allocated resources
  • • Resource Deallocation - Deallocate resources
  • • Resource Cleanup - Clean up resources

Resource Monitoring

  • • Resource Tracking - Track resource usage
  • • Resource Auditing - Audit resource operations
  • • Resource Reporting - Report resource status
  • • Resource Analysis - Analyze resource patterns

Error Recovery

  • • Error Detection - Detect resource errors
  • • Error Recovery - Recover from resource errors
  • • Retry Mechanisms - Implement retry logic
  • • Fallback Procedures - Use fallback procedures

Error Handling

Common Response Codes

  • DFHRESP(NORMAL) - Resource free operation successful
  • DFHRESP(NOTAUTH) - Not authorized to free resource
  • DFHRESP(INVREQ) - Invalid resource free request
  • DFHRESP(RESOURCEERR) - Resource free operation error
  • DFHRESP(RESOURCENOTFOUND) - Resource not found
  • DFHRESP(RESOURCEINUSE) - Resource is in use

Performance Considerations

Resource Efficiency

  • • Optimize resource operations - Use efficient resource handling
  • • Minimize resource overhead - Reduce resource processing overhead
  • • Use resource pooling - Implement resource pooling
  • • Monitor resource frequency - Track resource free patterns

System Impact

  • • Monitor system impact - Track how resource free affects the system
  • • Optimize resource handling - Ensure efficient resource processing
  • • Manage resource usage - Monitor resource consumption
  • • Track performance metrics - Monitor resource handling performance

Best Practices

Resource Deallocation Best Practices

  • • Free resources as soon as they are no longer needed
  • • Implement proper error handling for resource operations
  • • Validate resource state before freeing
  • • Use appropriate resource management techniques
  • • Monitor resource deallocation activities and performance
  • • Maintain resource deallocation audit trails
  • • Handle resource deallocation errors gracefully

Explain It Like I'm 5 Years Old

Think of CICS FREE like putting away your toys:

  • • Finished Playing: "You finished playing with your toys" - Resource no longer needed
  • • Put Away: "Put your toys away" - Free resource
  • • Clean Up: "Clean up your room" - Resource cleanup
  • • Room Clean: "Your room is clean now" - Resource freed
  • • Keep Clean: "Keep your room clean" - Resource management

Exercises

Exercise 1: Basic Resource Deallocation

Create a program that frees a basic resource.

Exercise 2: Advanced Resource Management

Write a program that manages multiple resource deallocations.

Exercise 3: Error Handling

Implement comprehensive error handling for resource deallocation failures.

Related Concepts

Resource Management

Managing system resources

Resource Deallocation

Deallocating resources

Resource Monitoring

Monitoring resource usage

Resource Cleanup

Cleaning up resources

Error Handling

Managing resource errors