Progress0 of 0 lessons

CICS PUSH HANDLE - Handler Stack Management

CICS PUSH HANDLE provides handler stack management capabilities in CICS environments. It enables programs to push handlers onto the stack, manage handler operations, and handle handler stack management for proper handler hierarchy control.

Command Syntax

cobol
1
2
3
4
       EXEC CICS PUSH HANDLE
            [RESP(response-code)]
            [RESP2(response-code-2)]
       END-EXEC.

Parameters

RESP(response-code)

Specifies the response code variable to receive the operation result. This parameter provides error handling and status information.

RESP2(response-code-2)

Specifies the secondary response code variable for additional error information. This parameter provides extended error details when available.

Handler Stack Operations

Handler Addition

PUSH HANDLE adds the current handler configuration to the handler stack, preserving the existing handler for later restoration.

Stack Management

The command manages the handler stack by maintaining proper handler hierarchy and ensuring correct handler activation order.

Handler Lifecycle

Handler lifecycle management ensures proper handler activation, preservation, and restoration for robust error handling.

Stack Integrity

Stack integrity maintenance ensures proper handler stack operation and prevents handler conflicts and resource issues.

Programming Examples

Basic Handler Pushing

cobol
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
       WORKING-STORAGE SECTION.
       01  RESPONSE-CODE     PIC S9(8) COMP.
       01  RESPONSE-CODE-2   PIC S9(8) COMP.
 
       PROCEDURE DIVISION.
           EXEC CICS PUSH HANDLE
                RESP(RESPONSE-CODE)
                RESP2(RESPONSE-CODE-2)
           END-EXEC
           
           IF RESPONSE-CODE = 0
               DISPLAY 'Handler pushed successfully'
               DISPLAY 'Current handler preserved on stack'
           ELSE
               DISPLAY 'Error pushing handler: ' RESPONSE-CODE
           END-IF.
           
           PERFORM SET-NEW-HANDLER
           PERFORM CONTINUE-PROCESSING.

Multiple Handler Pushing

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
       WORKING-STORAGE SECTION.
       01  RESPONSE-CODE     PIC S9(8) COMP.
       01  RESPONSE-CODE-2   PIC S9(8) COMP.
       01  PUSH-COUNT        PIC S9(8) COMP VALUE 0.
 
       PROCEDURE DIVISION.
           PERFORM PUSH-FILE-HANDLER
           PERFORM PUSH-DATA-HANDLER
           PERFORM PUSH-SYSTEM-HANDLER.
           
       PUSH-FILE-HANDLER.
           EXEC CICS PUSH HANDLE
                RESP(RESPONSE-CODE)
                RESP2(RESPONSE-CODE-2)
           END-EXEC
           IF RESPONSE-CODE = 0
               ADD 1 TO PUSH-COUNT
               DISPLAY 'File handler pushed'
           END-IF.
           
       PUSH-DATA-HANDLER.
           EXEC CICS PUSH HANDLE
                RESP(RESPONSE-CODE)
                RESP2(RESPONSE-CODE-2)
           END-EXEC
           IF RESPONSE-CODE = 0
               ADD 1 TO PUSH-COUNT
               DISPLAY 'Data handler pushed'
           END-IF.
           
       PUSH-SYSTEM-HANDLER.
           EXEC CICS PUSH HANDLE
                RESP(RESPONSE-CODE)
                RESP2(RESPONSE-CODE-2)
           END-EXEC
           IF RESPONSE-CODE = 0
               ADD 1 TO PUSH-COUNT
               DISPLAY 'System handler pushed'
           END-IF.

Dynamic Handler 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
       WORKING-STORAGE SECTION.
       01  RESPONSE-CODE     PIC S9(8) COMP.
       01  RESPONSE-CODE-2   PIC S9(8) COMP.
       01  PROCESSING-COUNT  PIC S9(8) COMP VALUE 0.
       01  MAX-PUSH-COUNT    PIC S9(8) COMP VALUE 3.
 
       PROCEDURE DIVISION.
           PERFORM VARYING PROCESSING-COUNT FROM 1 BY 1
           UNTIL PROCESSING-COUNT > MAX-PUSH-COUNT
               PERFORM PUSH-HANDLER
               PERFORM SET-NEW-HANDLER
           END-PERFORM.
           
       PUSH-HANDLER.
           EXEC CICS PUSH HANDLE
                RESP(RESPONSE-CODE)
                RESP2(RESPONSE-CODE-2)
           END-EXEC
           
           IF RESPONSE-CODE = 0
               DISPLAY 'Handler pushed successfully - count: ' PROCESSING-COUNT
           ELSE
               DISPLAY 'Error pushing handler: ' RESPONSE-CODE
           END-IF.
           
       SET-NEW-HANDLER.
           DISPLAY 'Setting new handler for processing step: ' PROCESSING-COUNT.

Error Handling

Response Code 0

Successful handler pushing. The handler has been successfully pushed onto the stack and is preserved for later restoration.

Response Code 8

Stack overflow. The handler stack has reached its maximum capacity and cannot accept additional handlers.

Response Code 12

Invalid handler stack. The handler stack is in an invalid state and cannot accept new handlers.

Response Code 16

Push operation failed. The handler pushing operation failed due to system conditions.

Response Code 20

Handler not available. The handler pushing capability is not available in the current execution context.

Performance Considerations

Stack Efficiency

PUSH HANDLE efficiently manages the handler stack, but excessive pushing operations may impact system performance.

Stack Management

Proper stack management ensures efficient handler operations and prevents stack overflow and resource exhaustion.

Handler Lifecycle

Handler lifecycle management ensures proper handler activation and preservation for optimal system performance.

Best Practices

Error Handling

Always check response codes and handle errors appropriately, especially for stack validation and handler availability.

Stack Management

Implement proper stack management strategies to ensure correct handler hierarchy and prevent stack-related errors.

Handler Lifecycle

Manage handler lifecycle properly by ensuring handlers are pushed and popped in the correct order and at appropriate times.

Stack Integrity

Maintain stack integrity by ensuring proper push/pop operations and preventing stack corruption.

Explain It Like I's 5 Years Old

Imagine you have a stack of plates, and you want to add another plate on top. CICS PUSH HANDLE is like putting a new plate on top of your stack of plates.

The handler stack is like your stack of plates, and each plate is like a different handler. When you push a handler, you put it on top of the stack so you can use it, but you keep the old ones underneath.

Just like you need to make sure you don't put too many plates on your stack (or it might fall over), the program needs to make sure it doesn't put too many handlers on the stack.

Exercises

Exercise 1: Basic Handler Pushing

Write a program that uses PUSH HANDLE to add a handler to the stack and verify the operation was successful.

Exercise 2: Multiple Handler Management

Create a program that manages multiple handlers by pushing and popping them in the correct order.

Exercise 3: Dynamic Stack Management

Implement a handler stack management system that dynamically pushes and pops handlers based on program requirements.

Related Concepts

CICS Handler Management

Understanding CICS handler management and stack operations

CICS Stack Management

Learning about CICS stack management and operations

CICS Error Handling

Understanding CICS error handling and recovery procedures

CICS Program Control

Learning about CICS program control and flow management