II04474: TERMINAL HUNG WITH X-CLOCK BUT CICS SHOWS NO ACTIVITY FOR THE TERMINAL

APAR status

• Closed as canceled.

Error description

• KEYWORDS: 566540301 5746XX300 5740XX100 R113 RG03
  RG02 RA69 566533301 R302
  ERROR MESSAGES:
  MSGDFH3405 CATASTROPHIC BRACKET ERROR SNS20030000
  MSGDFH2469 SNS20010000
  PROG498
  THE MAIN SYMPTOM OF THIS PROBLEM IS A TERMINAL IS HUNG WITH
  AN X-CLOCK, BUT CICS DOES NOT SHOW ANY ACTVITY FOR THE TERMINAL.
  WHEN CICS SENDS AN EB WITH EXCEPTION RESPONSE, IT DOESN'T WAIT
  FOR A RESPONSE FROM THE TERMINAL.  CICS UNCONDITIONALLY ENDS THE
  BRACKET AS SOON AS THE REQUEST IS SENT TO VTAM.  THIS PUTS CICS
  'BETWEEN BRACKETS' AND CICS WILL THEN WAIT FOR THE TERMINAL TO
  PROVIDE MORE INPUT (USUALLY THE USER HITTING THE ENTER KEY).
  IT IS AT THIS TIME THE TERMINAL IS HANGING WITH THE X-CLOCK.
  THIS IS CAUSED BY MONITOR PACKAGES COLLECTING TERMINAL RESPONSE
  TIME DATA.  THE IBM MONITOR THAT CAN CAUSE THIS TO HAPPEN IS
  NPM.  THERE ARE SEVERAL OEM MONITOR PACKAGES THAT PERFORM THE
  SAME FUNCTION IN THE SAME MANNER THUS CAUSING THIS PROBLEM.
  ***NPM USERS*** PLEASE CONTACT THE IBM SUPPORT CENTER IF
  YOU ARE HAVING THESE PROBLEMS WHEN USING NPM
  -
  THE MONITOR CAUSES THE PROBLEM BY CHANGING THE SEND OF THE EB
  EXCEPTION RESPONSE TO DEFINITE RESPONSE.  IF THE TERMINAL
  REJECTS THE SEND WITH A NEGATIVE RESPONSE AND THE REQUEST
  WAS SENT DEFINITE RESPONSE, PROTOCOL REQUIRES THE BRACKET TO
  CONTINUE.  AT THIS POINT THE TERMINAL WAITS FOR CICS TO TAKE
  FURTHER ACTION TO END THE BRACKET, KEEPING THE KEYBOARD
  INHIBITED UNTIL THE BRACKET IS ENDED.  HOWEVER, CICS WILL NOT
  TAKE FURTHER ACTION BECAUSE IT THINKS THE EB WAS SENT WITH
  EXCEPTION RESPONSE.  PROTOCOL ALLOWS CICS TO ASSUME THE BRACKET
  WAS ENDED BY THE TERMINAL.  THIS RESULTS IN THE TERMINAL
  WAITING FOR ACTION THAT CICS WILL NEVER TAKE.
  -
  CIRCUMVENTION: TURN OFF THE TERMINAL RESPONSE TIME COLLECTION.
  ***NPM USERS**** SEE INFO APAR II03836 FOR DDR FEATURE OF
  NPM FOR ADDITIONAL INFORMATION ON THIS PROBLEM.
  -
  BACKGROUND INFORMATION:
   1. WHY MONITORS CHANGE ER TO DR
  IN ORDER TO COLLECT TERMINAL RESPONSE TIME DATA, THE MONITOR
  PACKAGE NEEDS TO FIND OUT HOW LONG IT TAKES FROM THE POINT IN
  TIME WHEN A SCREEN IS SENT TO A TERMINAL UNTIL A RESPONSE IS
  RECEIVED FROM THE TERMINAL.  IN ORDER TO GET A RESPONSE BACK,
  THE SEND MUST BE DONE DEFINITE RESPONSE.  IF THE SEND LEAVES
  CICS AS EXCEPTION RESPONSE, THEN THE MONITOR CAN'T TIME IT.
  SO, THE MONITOR WILL CHANGE THE SEND FROM EXCEPTION TO DEFINITE.
  WHEN THE POSITIVE RESPONSE COMES BACK THE MONITOR WILL INTERCEPT
  IT AND PREVENT IT FROM GOING BACK TO CICS.  THIS WILL PREVENT
  'MSGDFH3465 UNEXPECTED RESPONSE RECEIVED' FROM BEING ISSUED.
   2. TERMINATION RULE #1
   VIOLATION OF THIS RULE IS WHAT CAUSES THE ERROR TO HAPPEN.
  THE SEND GOING TO THE TERMINAL IN OUR CASE CONTAINS END BRACKET
  (EB) COMMAND.  THIS INVOKES TERMINATION RULE 1 WHICH IS
  DOCUMENTED IN THE SYSTEMS NETWORK ARCHITECTURE FORMAT AND
  PROTOCOL REFERENCE MANUAL, NUMBER SC30-3112-2, PAGES 5-16,17.
   THE RULE STATES THAT IF THE EB IS SENT WITHOUT A BB ON IN THE
  SAME CHAIN, AND IT REQUESTS DEFINITE RESPONSE, 'THE BRACKET
  IS NOT TERMINATED UNTIL A POSITIVE RESPONSE IS PROCESSED.  A
  NEGATIVE RESPONSE TO THE LAST REQUEST CAUSES THE BRACKET TO BE
  CONTINUED.'  IF THE EB IS SENT WITHOUT A BB IN THE SAME CHAIN
  AND IT REQUESTS EXCEPTION RESPONSE, 'THE BRACKET IS TERMINATED
  UNCONDITIONALLY WHEN THE LAST REQUEST OF THE CHAIN...IS
  PROCESSED.'
  

Local fix

Problem summary

Problem conclusion

Temporary fix

Comments

• CLOSING CAN PER INFO APAR GUIDELINES.
  

APAR Information

• APAR is sysrouted FROM one or more of the following:

• APAR is sysrouted TO one or more of the following:

Fix information

Applicable component levels