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CICS FREEMAIN - Memory Deallocation

CICS FREEMAIN provides memory deallocation capabilities for programs and transactions. It enables programs to free allocated memory, manage memory cleanup, and handle memory deallocation in CICS environments.

What is CICS FREEMAIN?

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

Command Syntax

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EXEC CICS FREEMAIN
    [DATA(data-area)]
    [LENGTH(data-length)]
    [RESP(response-code)]
END-EXEC

Parameters

Optional Parameters

  • DATA(data-area) - Data area to free
  • LENGTH(data-length) - Length of data to free
  • RESP(response-code) - Response code variable

Memory Types

Main Storage

Main storage memory types

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

Memory Areas

Memory area types

  • • WORKING STORAGE - Working storage memory
  • • LINKAGE SECTION - Linkage section memory
  • • COMMUNICATION AREA - Communication area memory
  • • BUFFER AREA - Buffer area memory

Dynamic Memory

Dynamic memory types

  • • DYNAMIC STORAGE - Dynamic storage memory
  • • HEAP STORAGE - Heap storage memory
  • • STACK STORAGE - Stack storage memory
  • • TEMPORARY STORAGE - Temporary storage memory

System Memory

System memory types

  • • SYSTEM STORAGE - System storage memory
  • • USER STORAGE - User storage memory
  • • PROTECTED STORAGE - Protected storage memory
  • • COMMON STORAGE - Common storage memory

Programming Examples

Basic Memory Deallocation

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       IDENTIFICATION DIVISION.
       PROGRAM-ID. FREEMAIN01.
       DATA DIVISION.
       WORKING-STORAGE SECTION.
       01  DATA-AREA PIC X(100).
       01  DATA-LENGTH PIC S9(4) COMP VALUE 100.
       01  RESPONSE-CODE PIC S9(8) COMP.
       
       PROCEDURE DIVISION.
           DISPLAY 'Freeing memory'
           DISPLAY 'Data length: ' DATA-LENGTH
           
           EXEC CICS FREEMAIN
               DATA(DATA-AREA)
               LENGTH(DATA-LENGTH)
               RESP(RESPONSE-CODE)
           END-EXEC
           
           IF RESPONSE-CODE = DFHRESP(NORMAL)
               DISPLAY 'Memory freed successfully'
           ELSE
               DISPLAY 'Memory free failed'
           END-IF
           
           EXEC CICS RETURN END-EXEC.

Advanced Memory Management

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       IDENTIFICATION DIVISION.
       PROGRAM-ID. FREEMAIN02.
       DATA DIVISION.
       WORKING-STORAGE SECTION.
       01  DATA-AREA PIC X(100).
       01  DATA-LENGTH PIC S9(4) COMP VALUE 100.
       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  MEMORY-STATUS PIC X(1).
       01  MEMORY-LIST.
           05  MEMORY-ITEM OCCURS 3 TIMES.
               10  MEMORY-ID PIC X(8).
               10  MEMORY-SIZE PIC S9(4) COMP.
               10  MEMORY-STATUS PIC X(1).
       
       PROCEDURE DIVISION.
           PERFORM INITIALIZE-MEMORY
           PERFORM FREE-MULTIPLE-MEMORY
           
           EXEC CICS RETURN END-EXEC.
       
       INITIALIZE-MEMORY.
           MOVE 'MEM001' TO MEMORY-ID(1)
           MOVE 100 TO MEMORY-SIZE(1)
           MOVE 'MEM002' TO MEMORY-ID(2)
           MOVE 200 TO MEMORY-SIZE(2)
           MOVE 'MEM003' TO MEMORY-ID(3)
           MOVE 300 TO MEMORY-SIZE(3).
       
       FREE-MULTIPLE-MEMORY.
           PERFORM VARYING FREE-COUNT FROM 1 BY 1
               UNTIL FREE-COUNT > MAX-FREES
               
               MOVE MEMORY-SIZE(FREE-COUNT) TO DATA-LENGTH
               PERFORM FREE-SINGLE-MEMORY
               
               IF RESPONSE-CODE = DFHRESP(NORMAL)
                   MOVE 'F' TO MEMORY-STATUS(FREE-COUNT)
                   DISPLAY 'Memory ' FREE-COUNT ' freed successfully'
               ELSE
                   MOVE 'E' TO MEMORY-STATUS(FREE-COUNT)
                   DISPLAY 'Memory ' FREE-COUNT ' free failed'
               END-IF
           END-PERFORM.
       
       FREE-SINGLE-MEMORY.
           EXEC CICS FREEMAIN
               DATA(DATA-AREA)
               LENGTH(DATA-LENGTH)
               RESP(RESPONSE-CODE)
           END-EXEC.

Error Handling with Memory Deallocation

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       IDENTIFICATION DIVISION.
       PROGRAM-ID. FREEMAIN03.
       DATA DIVISION.
       WORKING-STORAGE SECTION.
       01  DATA-AREA PIC X(100).
       01  DATA-LENGTH PIC S9(4) COMP VALUE 100.
       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  MEMORY-FREE-SUCCESSFUL PIC X(1) VALUE 'N'.
       
       PROCEDURE DIVISION.
           PERFORM FREE-MEMORY-WITH-RETRY
           
           EXEC CICS RETURN END-EXEC.
       
       FREE-MEMORY-WITH-RETRY.
           PERFORM FREE-MEMORY
           
           IF RESPONSE-CODE NOT = DFHRESP(NORMAL)
               AND RETRY-COUNT < MAX-RETRIES
               ADD 1 TO RETRY-COUNT
               DISPLAY 'Retry ' RETRY-COUNT ' memory free operation'
               PERFORM FREE-MEMORY-WITH-RETRY
           END-IF.
       
       FREE-MEMORY.
           EXEC CICS FREEMAIN
               DATA(DATA-AREA)
               LENGTH(DATA-LENGTH)
               RESP(RESPONSE-CODE)
           END-EXEC
           
           EVALUATE RESPONSE-CODE
               WHEN DFHRESP(NORMAL)
                   MOVE 'Y' TO MEMORY-FREE-SUCCESSFUL
                   DISPLAY 'Memory free operation successful'
               WHEN DFHRESP(NOTAUTH)
                   DISPLAY 'Not authorized to free memory'
               WHEN DFHRESP(INVREQ)
                   DISPLAY 'Invalid memory free request'
               WHEN DFHRESP(MEMORYERR)
                   DISPLAY 'Memory free operation error'
               WHEN DFHRESP(MEMORYNOTFOUND)
                   DISPLAY 'Memory not found'
               WHEN DFHRESP(MEMORYINUSE)
                   DISPLAY 'Memory is in use'
               WHEN OTHER
                   DISPLAY 'Unexpected memory free error'
           END-EVALUATE.

Memory Management

Memory Deallocation

  • • Memory Free - Free allocated memory
  • • Memory Cleanup - Clean up memory state
  • • Memory Validation - Validate memory state
  • • Memory Monitoring - Monitor memory status

Memory Lifecycle

  • • Memory Allocation - Allocate memory
  • • Memory Usage - Use allocated memory
  • • Memory Deallocation - Deallocate memory
  • • Memory Cleanup - Clean up memory

Memory Monitoring

  • • Memory Tracking - Track memory usage
  • • Memory Auditing - Audit memory operations
  • • Memory Reporting - Report memory status
  • • Memory Analysis - Analyze memory patterns

Error Recovery

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

Error Handling

Common Response Codes

  • DFHRESP(NORMAL) - Memory free operation successful
  • DFHRESP(NOTAUTH) - Not authorized to free memory
  • DFHRESP(INVREQ) - Invalid memory free request
  • DFHRESP(MEMORYERR) - Memory free operation error
  • DFHRESP(MEMORYNOTFOUND) - Memory not found
  • DFHRESP(MEMORYINUSE) - Memory is in use

Performance Considerations

Memory Efficiency

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

System Impact

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

Best Practices

Memory Deallocation Best Practices

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

Explain It Like I'm 5 Years Old

Think of CICS FREEMAIN like putting away your memory toys:

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

Exercises

Exercise 1: Basic Memory Deallocation

Create a program that frees basic memory.

Exercise 2: Advanced Memory Management

Write a program that manages multiple memory deallocations.

Exercise 3: Error Handling

Implement comprehensive error handling for memory deallocation failures.

Related Concepts

Memory Management

Managing system memory

Memory Deallocation

Deallocating memory

Memory Monitoring

Monitoring memory usage

Memory Cleanup

Cleaning up memory

Error Handling

Managing memory errors