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CICS LINK - Link

CICS LINK provides link management capabilities, enabling link processing and output processing in CICS environments. It provides efficient link capabilities for CICS applications.

What is CICS LINK?

CICS LINK provides link management capabilities, enabling link processing and output processing. It provides efficient link capabilities, allowing applications to manage link operations.

Command Syntax

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EXEC CICS LINK
    [RESP(response-code)]
    [RESP2(response-code-2)]
END-EXEC.

Parameters Explained

RESP Parameters

Response codes returned by the command:

  • RESP: Primary response code - indicates the success or failure of the link operation
  • RESP2: Secondary response code - provides additional error information when RESP indicates failure
  • Always check these codes for command success before proceeding with data processing
  • Handle command failures appropriately to prevent application errors

Link Types

1. Basic Links

  • Basic links: Standard link operations that handle simple connections without special formatting
  • Mapped links: Link operations that use predefined field mappings to structure link data
  • Unmapped links: Raw link operations that handle unstructured connections without predefined field mappings
  • Custom links: Specialized link operations designed for specific application requirements

2. Advanced Links

  • Advanced links: Complex link operations that handle sophisticated connection processing and validation
  • Secure links: Link operations that include encryption and security features for sensitive connections
  • Encrypted links: Link operations that automatically encrypt link data
  • Compressed links: Link operations that handle compressed connection streams and automatically compress link data

3. Specialized Links

  • Specialized links: Link operations tailored for specific protocols or communication methods
  • High-performance links: Optimized link operations designed for maximum throughput and efficiency
  • Low-latency links: Link operations optimized for minimal delay and real-time processing requirements
  • High-throughput links: Link operations designed to handle large volumes of connections efficiently

Implementation Example

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WORKING-STORAGE SECTION.
01 WS-RESPONSE            PIC S9(8) COMP.
01 WS-RESPONSE2           PIC S9(8) COMP.
 
PROCEDURE DIVISION.
    * Link operation
    EXEC CICS LINK
        RESP(WS-RESPONSE)
        RESP2(WS-RESPONSE2)
    END-EXEC.
    
    IF WS-RESPONSE NOT EQUAL DFHRESP(NORMAL)
        EXEC CICS WRITE OPERATOR
            TEXT('LINK command failed')
        END-EXEC
        EXEC CICS RETURN END-EXEC
    END-IF.
    
    * Link operation completed successfully
    * Continue processing

Link Processing

1. Link Preparation

Link preparation includes:

  • Link validation - ensuring the link operation is properly configured and authorized
  • Link formatting - preparing data structures and buffers for link data
  • Link encoding - setting up proper character encoding and data transformation
  • Link processing - initializing the link operation and preparing for connection

2. Link Transmission

Link transmission includes:

  • Link routing - directing link data to the appropriate processing location
  • Link delivery - ensuring link data reaches the correct destination within the application
  • Transmission confirmation - verifying that link was completed successfully
  • Error handling - managing transmission failures and implementing retry mechanisms

3. Output Management

Output management includes:

  • User management - handling user sessions and maintaining connection state
  • Output formatting - structuring link data for presentation or further processing
  • User experience - ensuring smooth data flow and responsive application behavior
  • Performance optimization - maximizing link efficiency and minimizing resource usage

Common Response Codes

Success Response Codes

  • NORMAL (0): Link operation completed successfully - connection was established without errors
  • LINK (4): Link operation completed - operation completed with link-specific status

Error Response Codes

  • INVREQ (16): Invalid request - the link operation parameters are incorrect or unauthorized
  • NOTFND (20): Resource not found - the specified link resource does not exist
  • LENGERR (22): Length error - the link data length exceeds expected limits
  • LINK (24): Link error - a link-specific error occurred during the operation

Best Practices

1. Link Preparation

  • Prepare link appropriately - ensure all necessary resources and configurations are in place
  • Validate link content - verify that link data meets expected format and quality standards
  • Handle different link types - implement flexible processing to accommodate various connection formats
  • Ensure link integrity - maintain data consistency and prevent corruption during connection

2. Error Handling

  • Check all response codes - always examine both RESP and RESP2 for complete error information
  • Handle link failures - implement appropriate recovery mechanisms for failed link operations
  • Implement retry logic - provide automatic retry capabilities for transient failures
  • Log error conditions - maintain detailed logs for troubleshooting and monitoring purposes

3. Performance Optimization

  • Minimize link operations - reduce unnecessary link calls to improve overall performance
  • Use efficient link formats - choose appropriate data formats to minimize processing overhead
  • Optimize user updates - streamline user interface updates to reduce response time
  • Manage user resources - efficiently allocate and manage system resources for link operations

Explain It Like I'm 5 Years Old

Imagine you're connecting two toys:

When you want to connect two toys, you take a string and tie one end to one toy and the other end to the other toy. If the string is tied tightly, the toys are connected. If the string is not tied tightly, the toys are not connected.

CICS LINK is like connecting two toys. The computer program takes a string and ties one end to one program and the other end to the other program. If the string is tied tightly, the programs are connected. If the string is not tied tightly, the programs are not connected.

Just like you connect toys, the computer program connects programs!

Exercises

Exercise 1: Link Operation

Write a CICS LINK command to perform a link operation.

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EXEC CICS LINK
    RESP(WS-RESPONSE)
    RESP2(WS-RESPONSE2)
END-EXEC.

Exercise 2: Link Processing

How would you implement comprehensive link processing that handles different link types and requirements?

Answer: Identify different link types and appropriate handling, implement link validation and encoding, handle different link types and capabilities, implement proper error handling for link failures, optimize link operations for performance, and maintain link integrity throughout the process.

Quiz

Question 1

What is the primary purpose of CICS LINK?

Answer: B) To provide link management capabilities

Question 2

Which parameter specifies the response code?

Answer: A) RESP

Related Concepts

CICS Link Processing

Link processing and output in CICS

CICS User Management

User management and user interaction in CICS

CICS Output Processing

Output processing and link display in CICS