What are the different synchronization levels in APPC ALLOCATE?

APPC ALLOCATE supports different synchronization levels including NONE (no synchronization), CONFIRM (confirmation required), SYNCLEVEL (full synchronization), and FLUSH (flush synchronization).

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

Always check the response code from ALLOCATE and implement appropriate error handling, including retry logic for transient failures and proper resource cleanup on allocation failures.

What conversation states are available in APPC ALLOCATE?

APPC ALLOCATE supports various conversation states including SEND (send state), RECEIVE (receive state), SEND/RECEIVE (both states), and RESET (reset state) for different communication modes.

When should I use CICS ALLOCATE (APPC)?

Use CICS ALLOCATE (APPC) when you need to establish APPC communication sessions, allocate conversation resources, or manage inter-system communication in distributed CICS applications.

CICS ALLOCATE (APPC) - APPC Resource Allocation

Q: What is CICS ALLOCATE (APPC) command used for?

CICS ALLOCATE (APPC) is used to allocate APPC resources, establish communication sessions, and manage conversation resources for Advanced Program-to-Program Communication in CICS environments.

CICS ALLOCATE (APPC) provides Advanced Program-to-Program Communication resource allocation capabilities in CICS environments. It enables programs to establish APPC sessions, allocate conversation resources, and manage APPC communication in distributed applications.

What is CICS ALLOCATE (APPC)?

CICS ALLOCATE (APPC) is a command that allows programs to allocate APPC resources, establish communication sessions, and manage conversation resources in CICS environments. It provides session management capabilities, resource allocation, and conversation establishment for distributed applications.

Command Syntax

cobol

1
2
3
4
5
6
7
EXEC CICS ALLOCATE
    SESSION(session-name)
    CONVID(conversation-id)
    SYNCLEVEL(sync-level)
    STATE(state-value)
    RESP(response-code)
END-EXEC

Parameters

Required Parameters

SESSION - Name of the APPC session to allocate
CONVID - Conversation ID for the allocated session

Optional Parameters

SYNCLEVEL - Synchronization level for the conversation
STATE - Initial state of the conversation
RESP - Response code variable

APPC Session Management

Session Allocation

Establishing APPC sessions

• Resource allocation
• Session establishment
• Connection setup
• State initialization

Conversation Management

Managing APPC conversations

• Conversation ID assignment
• State management
• Resource tracking
• Lifecycle control

Synchronization Levels

Different sync levels

• NONE - No synchronization
• CONFIRM - Confirmation required
• SYNCLEVEL - Full synchronization
• FLUSH - Flush synchronization

Resource States

Conversation states

• SEND - Send state
• RECEIVE - Receive state
• SEND/RECEIVE - Both states
• RESET - Reset state

Programming Examples

Basic APPC Allocation

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
       IDENTIFICATION DIVISION.
       PROGRAM-ID. ALLOCATE01.
       DATA DIVISION.
       WORKING-STORAGE SECTION.
       01  SESSION-NAME     PIC X(8) VALUE 'APPC001'.
       01  CONVERSATION-ID  PIC X(8).
       01  SYNC-LEVEL       PIC S9(4) COMP VALUE 0.
       01  STATE-VALUE      PIC S9(4) COMP VALUE 0.
       01  RESPONSE-CODE    PIC S9(8) COMP.
       
       PROCEDURE DIVISION.
           EXEC CICS ALLOCATE
               SESSION(SESSION-NAME)
               CONVID(CONVERSATION-ID)
               SYNCLEVEL(SYNC-LEVEL)
               STATE(STATE-VALUE)
               RESP(RESPONSE-CODE)
           END-EXEC
           
           IF RESPONSE-CODE = DFHRESP(NORMAL)
               DISPLAY 'APPC session allocated successfully'
               DISPLAY 'Conversation ID: ' CONVERSATION-ID
           ELSE
               DISPLAY 'Failed to allocate APPC session'
           END-IF
           
           EXEC CICS RETURN END-EXEC.

Advanced APPC Allocation

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
       IDENTIFICATION DIVISION.
       PROGRAM-ID. ALLOCATE02.
       DATA DIVISION.
       WORKING-STORAGE SECTION.
       01  SESSION-NAME     PIC X(8) VALUE 'APPC002'.
       01  CONVERSATION-ID  PIC X(8).
       01  SYNC-LEVEL       PIC S9(4) COMP VALUE 1.
       01  STATE-VALUE      PIC S9(4) COMP VALUE 1.
       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.
       
       PROCEDURE DIVISION.
           PERFORM ALLOCATE-SESSION WITH TEST AFTER
               UNTIL RESPONSE-CODE = DFHRESP(NORMAL)
               OR RETRY-COUNT >= MAX-RETRIES
           
           IF RESPONSE-CODE = DFHRESP(NORMAL)
               DISPLAY 'APPC session allocated with sync level'
               DISPLAY 'Conversation ID: ' CONVERSATION-ID
           ELSE
               DISPLAY 'Failed to allocate APPC session after retries'
           END-IF
           
           EXEC CICS RETURN END-EXEC.
       
       ALLOCATE-SESSION.
           ADD 1 TO RETRY-COUNT
           
           EXEC CICS ALLOCATE
               SESSION(SESSION-NAME)
               CONVID(CONVERSATION-ID)
               SYNCLEVEL(SYNC-LEVEL)
               STATE(STATE-VALUE)
               RESP(RESPONSE-CODE)
           END-EXEC
           
           IF RESPONSE-CODE NOT = DFHRESP(NORMAL)
               DISPLAY 'Allocation attempt ' RETRY-COUNT ' failed'
           END-IF.

Error Handling with APPC Allocation

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
       IDENTIFICATION DIVISION.
       PROGRAM-ID. ALLOCATE03.
       DATA DIVISION.
       WORKING-STORAGE SECTION.
       01  SESSION-NAME     PIC X(8) VALUE 'APPC003'.
       01  CONVERSATION-ID  PIC X(8).
       01  RESPONSE-CODE    PIC S9(8) COMP.
       
       PROCEDURE DIVISION.
           EXEC CICS ALLOCATE
               SESSION(SESSION-NAME)
               CONVID(CONVERSATION-ID)
               RESP(RESPONSE-CODE)
           END-EXEC
           
           EVALUATE RESPONSE-CODE
               WHEN DFHRESP(NORMAL)
                   DISPLAY 'APPC session allocated successfully'
               WHEN DFHRESP(NOTFND)
                   DISPLAY 'Session not found'
               WHEN DFHRESP(INVREQ)
                   DISPLAY 'Invalid allocation request'
               WHEN DFHRESP(NOSPACE)
                   DISPLAY 'No space available for allocation'
               WHEN DFHRESP(APPCERR)
                   DISPLAY 'APPC-specific error occurred'
               WHEN OTHER
                   DISPLAY 'Unexpected error occurred'
           END-EVALUATE
           
           EXEC CICS RETURN END-EXEC.

APPC Resource Management

Resource Allocation

• Session resource allocation
• Conversation ID assignment
• State initialization
• Resource tracking

Session Lifecycle

• Allocation phase
• Active phase
• Deallocation phase
• Cleanup phase

State Management

• Initial state setting
• State transitions
• State validation
• State monitoring

Error Recovery

• Allocation failure handling
• Resource cleanup
• Retry mechanisms
• Error reporting

Error Handling

Common Response Codes

DFHRESP(NORMAL) - APPC session allocated successfully
DFHRESP(NOTFND) - Session not found
DFHRESP(INVREQ) - Invalid allocation request
DFHRESP(NOSPACE) - No space available for allocation
DFHRESP(APPCERR) - APPC-specific error
DFHRESP(INVREQ) - Invalid synchronization level

Performance Considerations

Resource Usage

• Monitor resource consumption
• Optimize allocation patterns
• Manage session pools
• Track resource utilization

Session Management

• Efficient session reuse
• Proper cleanup procedures
• Connection pooling
• Resource monitoring

Best Practices

APPC Allocation Best Practices

• Always check response codes
• Use appropriate synchronization levels
• Implement proper error handling
• Manage resource lifecycle properly
• Monitor session usage
• Implement retry logic for transient failures
• Clean up resources when done

Explain It Like I'm 5 Years Old

Think of CICS ALLOCATE (APPC) like setting up a phone call:

• Session: "Pick up the phone" - Establish a connection
• Conversation: "Start talking" - Begin the communication
• Sync Level: "Make sure they heard you" - Confirm the message was received
• State: "Are you listening or talking?" - Set the communication mode
• Allocation: "Get ready to talk" - Prepare for communication

Exercises

Exercise 1: Basic APPC Allocation

Create a program that allocates an APPC session with basic parameters.

Exercise 2: Advanced Session Management

Write a program that allocates an APPC session with synchronization and state management.

Exercise 3: Error Handling

Implement comprehensive error handling for APPC allocation failures.

CICS ALLOCATE (APPC) - APPC Resource Allocation

What is CICS ALLOCATE (APPC)?

Command Syntax

Parameters

Required Parameters

Optional Parameters

APPC Session Management

Session Allocation

Conversation Management

Synchronization Levels

Resource States

Programming Examples

Basic APPC Allocation

Advanced APPC Allocation

Error Handling with APPC Allocation

APPC Resource Management

Resource Allocation

Session Lifecycle

State Management

Error Recovery

Error Handling

Common Response Codes

Performance Considerations

Resource Usage

Session Management

Best Practices

APPC Allocation Best Practices

Explain It Like I'm 5 Years Old

Exercises

Exercise 1: Basic APPC Allocation

Exercise 2: Advanced Session Management

Exercise 3: Error Handling

Related Concepts

APPC Communication

Session Management

Resource Allocation

Inter-System Communication

Error Handling

Related Pages