Intermediate IBM MQ interviews assume you have configured queues and channels in a lab or non-production environment and can reason about failures from symptoms. Expect questions on sender-receiver pairs, transmission queues, CHLAUTH and MCAUSER, syncpoint with databases, cluster basics, request/reply correlation, and when to choose pub/sub versus point-to-point. Answers should mention specific objects and commands—not only theory—and acknowledge operational impact (depth, retry, DLQ).
The sender channel (SDR) runs on the queue manager that has messages to ship; it reads from a transmission queue (XMITQ) and connects outbound to the partner. The receiver channel (RCVR) runs on the target queue manager and accepts the inbound connection. Channel names must match on both sides; CHLTYPE differs. CONNAME on the sender points to host and port where the listener waits.
A transmission queue holds messages destined for a remote queue manager until the sender channel successfully transfers them. If the channel is not RUNNING, depth on the XMITQ grows—operations monitor it alongside the application queue on the source system.
Partner listener up, channel name match, CHLAUTH rules, TLS cipher and certificate trust, firewall port, and MCAUSER authority on the receiver. DISPLAY CHSTATUS on both queue managers; AMQERR logs on the side that refuses the handshake.
| Attribute | Effect | If mis-set |
|---|---|---|
| BATCHSZ | Messages per network batch | Latency vs throughput |
| BATCHINT | Max wait to fill batch | Slow link underutilized |
| HBINT | Heartbeat interval | False failure detection |
| DISCINT | Idle disconnect | Channel stop/start churn |
Channel authentication records control who may start channels and under which MCAUSER identity inbound connections run. When CHLAUTH is ENABLED, default rules often block unless you define scoped ALLOW rules for known partners. BLOCKUSER rules deny specific asserted users.
OAM (Object Authority Manager) controls access to queues, topics, and other objects—can this user put to PAY.Q? CHLAUTH controls channel binding—may this remote connection use this SVRCONN or start this SDR? Both are required for defense in depth.
1234DISPLAY CHSTATUS('PARTNER.SDR') CHSTATUS SUBSTATE DISPLAY CHLAUTH(*) WHERE(CHLTYPE EQ SVRCONN) * CHSTATUS — BINDING, RUNNING, RETRYING, etc. * SUBSTATE — more detail during failures
So both commit or both roll back. If the database commits but MQ fails, or vice versa, business data and messages disagree. MQCONN with syncpoint, MQPUT under UOW, SQL commit via resource manager, then MQCMIT—or MQBACK on error.
The message is rolled back to the queue and available again—at-least-once delivery. Consumers must be idempotent for financial processing.
The requester sets ReplyToQ and ReplyToQMgr in MQMD (or uses a fixed reply queue), puts the request, then GETs the reply queue with MatchOptions on CorrelId equal to the request MsgId. The responder copies CorrelId from the request into the reply. Timeouts prevent infinite wait.
Clusters automate routing and channel definitions between queue managers in the same cluster name. New queue managers join the cluster repository; cluster queues appear with workload balancing instead of defining every remote queue manually.
Full repository queue managers hold complete cluster object knowledge; partial repositories cache subset and consult full repos for updates. Misconfigured repositories cause routing inconsistencies—DISPLAY CLUSQMGR and cluster cache refresh skills matter in support roles.
A subscription that survives subscriber application downtime. Messages accumulate on the subscriber queue until the consumer returns. Non-durable subscriptions exist only while the application is subscribed.
Intermediate level is about the pipes between buildings (channels), who may open doors (CHLAUTH), and contracts that say water delivery and ledger entry happen together (syncpoint)—not just buckets (queues) inside one building.
Now you learn how mail trucks drive between towns (channels), who is allowed to drive in (security), and how to send a letter and wait for an answer letter back (request/reply).
Configure SDR/RCVR pair in lab; break TLS and document BINDING vs RUNNING fix steps.
Implement request/reply with amqsput/amqsget using correlation.
Explain idempotency to an interviewer in under sixty seconds.
1. Sender channel requires:
2. CHLAUTH ENABLED with no rules typically:
3. Syncpoint commit on GET means:
4. Cluster repository holds: