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CICS WAIT - Wait Processing

CICS WAIT suspends program execution until a specific event occurs or a timeout period expires in CICS environments. It enables event synchronization, process coordination, and efficient resource utilization.

What is CICS WAIT?

CICS WAIT suspends program execution until a specific event occurs or a timeout period expires. It enables event synchronization, process coordination, and efficient resource utilization by allowing programs to wait for specific conditions without consuming CPU resources.

Command Syntax

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EXEC CICS WAIT
    [EVENT(event-name)]
    [TIME(timeout-value)]
    [RESP(response-code)]
    [RESP2(response-code-2)]
END-EXEC.

Parameters Explained

EVENT Parameter

Specifies the event to wait for:

  • Optional parameter
  • Identifies specific event
  • Used for event synchronization
  • Can be omitted for general wait

TIME Parameter

Specifies the timeout period:

  • Optional parameter
  • Specifies maximum wait time
  • Used for timeout handling
  • Prevents indefinite waiting

RESP Parameters

Response codes returned by the command:

  • RESP: Primary response code
  • RESP2: Secondary response code
  • Always check these codes for command success
  • Handle command failures appropriately

Wait Types

1. Event Wait

  • Specific event: Wait for specific event
  • Event synchronization: Synchronize with events
  • Process coordination: Coordinate processes
  • Resource availability: Wait for resources

2. Time Wait

  • Timeout wait: Wait with timeout
  • Periodic wait: Wait for specific period
  • Delay wait: Wait for delay
  • Schedule wait: Wait for scheduled time

3. General Wait

  • Indefinite wait: Wait indefinitely
  • Condition wait: Wait for condition
  • Resource wait: Wait for resource
  • Status wait: Wait for status change

Implementation Example

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WORKING-STORAGE SECTION.
01 WS-RESPONSE            PIC S9(8) COMP.
01 WS-RESPONSE2           PIC S9(8) COMP.
01 WS-EVENT-NAME          PIC X(8) VALUE 'DATAREADY'.
01 WS-TIMEOUT             PIC S9(8) COMP VALUE 60.
 
PROCEDURE DIVISION.
    * Wait for specific event with timeout
    EXEC CICS WAIT
        EVENT(WS-EVENT-NAME)
        TIME(WS-TIMEOUT)
        RESP(WS-RESPONSE)
        RESP2(WS-RESPONSE2)
    END-EXEC.
    
    IF WS-RESPONSE EQUAL DFHRESP(TIMEOUT)
        EXEC CICS WRITE OPERATOR
            TEXT('Wait timeout occurred')
        END-EXEC
    ELSE IF WS-RESPONSE NOT EQUAL DFHRESP(NORMAL)
        EXEC CICS WRITE OPERATOR
            TEXT('WAIT command failed')
        END-EXEC
        EXEC CICS RETURN END-EXEC
    END-IF.
    
    * Wait completed successfully
    * Continue processing

Wait Processing

1. Event Detection

Event detection includes:

  • Event monitoring
  • Event recognition
  • Event validation
  • Event processing

2. Timeout Handling

Timeout handling includes:

  • Timeout detection
  • Timeout processing
  • Timeout recovery
  • Timeout notification

3. Resource Management

Resource management includes:

  • Resource allocation
  • Resource monitoring
  • Resource release
  • Resource optimization

Common Response Codes

Success Response Codes

  • NORMAL (0): Wait completed successfully
  • WAIT (4): Wait processed

Error Response Codes

  • INVREQ (16): Invalid request
  • TIMEOUT (20): Timeout occurred
  • EVENT (22): Event error
  • WAIT (24): Wait error

Best Practices

1. Wait Design

  • Use appropriate wait types
  • Set reasonable timeouts
  • Handle timeout conditions
  • Implement fallback procedures

2. Error Handling

  • Check all response codes
  • Handle wait failures
  • Implement retry logic
  • Log error conditions

3. Performance Optimization

  • Minimize wait times
  • Use efficient wait mechanisms
  • Optimize resource usage
  • Monitor wait performance

Explain It Like I'm 5 Years Old

Imagine you're waiting for your friend to arrive:

Sometimes you need to wait for your friend to arrive before you can start playing. You might wait by the door, or you might set a timer so you don't wait forever. If your friend doesn't come by the time the timer goes off, you might decide to do something else.

CICS WAIT is like waiting for your friend. The computer program waits for something to happen (like your friend arriving), and it can set a timer so it doesn't wait forever. If the timer goes off before what it's waiting for happens, it can decide to do something else.

Just like you wouldn't want to wait forever for your friend, the computer program doesn't want to wait forever either - it needs to know when to stop waiting and do something else!

Exercises

Exercise 1: Event Wait

Write a CICS WAIT command to wait for event 'DATAREADY' with a 30-second timeout.

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EXEC CICS WAIT
    EVENT('DATAREADY')
    TIME(30)
    RESP(WS-RESPONSE)
    RESP2(WS-RESPONSE2)
END-EXEC.

Exercise 2: Wait Coordination

How would you implement a wait coordination system where multiple processes need to synchronize their execution?

Answer: Define synchronization events for process coordination, implement event signaling between processes, use appropriate timeout values, handle timeout conditions with fallback procedures, implement error handling for wait failures, and monitor wait performance for optimization.

Quiz

Question 1

What is the primary purpose of CICS WAIT?

Answer: B) To suspend execution until event occurs

Question 2

Which parameter specifies the timeout period?

Answer: A) TIME

Related Concepts

CICS Event Processing

Event processing and event-driven architecture in CICS

CICS Process Synchronization

Process synchronization and coordination in CICS

CICS Resource Management

Resource management and optimization in CICS