SHORTTMR (Short Retry Timer)

When an IBM MQ message channel enters RETRY, the queue manager does not immediately give up—it schedules another connection attempt. SHORTRTY decides how many quick tries to make; SHORTTMR decides how many seconds to wait between those tries. A channel with SHORTRTY(10) and SHORTTMR(60) might spend roughly ten minutes in aggressive reconnect before long retry spacing applies. Operators who only raise SHORTRTY without understanding SHORTTMR accidentally create reconnect storms that overwhelm partner listeners. This tutorial explains SHORTTMR in seconds, how it interacts with SHORTRTY and LONGTMR, when to shorten or lengthen the interval, and how to diagnose RETRY loops that are tuning problems versus broken CONNAME or TLS.

Short Phase Timing in Plain Terms

Think of SHORTTMR as the pause between knocks on a door. SHORTRTY is how many knocks in the quick phase. If SHORTTMR is 10 seconds and SHORTRTY is 6, the short phase lasts about one minute of active retry scheduling before long retry backoff—arithmetic is approximate because processing and network time add overhead. Payment routes needing fast recovery after a thirty-second listener bounce might use SHORTTMR 20–60. Bulk routes to a partner under maintenance should not use SHORTTMR 5 with huge SHORTRTY—that punishes the partner network for hours.

Defining SHORTTMR in MQSC

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DEFINE CHANNEL('QM1.TO.QM2') CHLTYPE(SDR) TRPTYPE(TCP) +
  CONNAME('qm2.corp(1414)') XMITQ('XMIT.QM2') +
  SHORTRTY(10) SHORTTMR(30) LONGRTY(999999999) LONGTMR(600)
ALTER CHANNEL('QM1.TO.QM2') CHLTYPE(SDR) SHORTTMR(60)
DISPLAY CHANNEL('QM1.TO.QM2') SHORTRTY SHORTTMR LONGRTY LONGTMR
DISPLAY CHSTATUS('QM1.TO.QM2') STATUS LASTCHLERR

ALTER SHORTTMR affects new retry scheduling after the change; a channel already in RETRY may continue prior timing until the instance cycles—verify on your release. Record baseline SHORTRTY and SHORTTMR pairs per route in the operations manual so DR restores do not accidentally deploy lab values to production.

Explainer: Waiting Between Phone Redials

SHORTTMR is how long you wait before redialing when your friend did not answer—short enough to catch them if they just rebooted the phone, not so fast that you block their line with endless rings.

SHORTTMR vs HBINT vs BATCHINT

Beginners mix timer attributes because all are numbers on DISPLAY CHANNEL. HBINT is heartbeat interval for liveness on RUNNING channels—seconds between “still alive” checks. BATCHINT is milliseconds waiting to fill a message batch. SHORTTMR is seconds between reconnect attempts in RETRY. Changing HBINT does not fix RETRY caused by wrong CONNAME; lowering SHORTTMR does not fix silent TCP death—that is HBINT and network policy.

Tuning Guidelines

• Critical routes: SHORTTMR 30–120 if partner agrees; monitor listener load.
• Maintenance windows: STOP or PAUSE channel instead of SHORTTMR 1.
• Partner complaint of connection storms: increase SHORTTMR or reduce SHORTRTY.
• Flaky WiFi VPN paths: moderate SHORTTMR may help; fix VPN stability first.

XMITQ Growth During RETRY

Messages keep arriving on the transmission queue while SHORTTMR drives reconnect attempts. Alert on CURDEPTH and RETRY duration together. SHORTTMR does not throttle application puts—it only spaces channel reconnects. Back-pressure belongs in application design or partner coordination, not infinite fast retry.

Operational Checklist

1. DISPLAY CHSTATUS — STATUS RETRY, LASTCHLERR, time in state.
2. Test TCP and listener before changing SHORTTMR.
3. Compare SHORTTMR to partner maintenance notification length.
4. After fix, confirm RUNNING and XMITQ drain rate.
5. Post-mortem: was short phase too short or too long for actual outage?

Explain Like I'm Five: SHORTTMR

SHORTTMR is how many seconds MQ waits before trying again to connect when the first tries did not work.

Practice Exercises

Exercise 1

SHORTRTY=12, SHORTTMR=25. Estimate short-phase wall-clock time.

Exercise 2

Partner asks you to stop “hammering” port 1414. Which two attributes do you adjust first?

Exercise 3

Explain why SHORTTMR is in seconds but BATCHINT is in milliseconds.

Frequently Asked Questions

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