Multi-Hopping

What is Multi-hopping?

Passing a message from source to destination with one or more intermediate systems is called multi-hopping.

IBM MQ imeplements multi-hopping using queue manager alias

Consider you want to send a message from QM1 to QM3 through QM2(QM1->QM2->QM3).

create the queue managers QM1, QM2, QM3 using CRTMQM and start them using STRMQM.
create a remote queue, transmission queue and sender chnanel in QM1

runmqsc QM1

Remote queue:

DEFINE QREMOTE ('QM1.QR') +
       DESCR('Remote Q to send message to QL in QM3') +
       PUT(ENABLED) +
       DEFPRTY(0) +
       DEFPSIST(YES) +
       SCOPE(QMGR) +
       RQMNAME(QM2) +
       RNAME('QM3.QL') +
       XMITQ(QM2.XMITQ)

Transmission queue:

DEFINE QLOCAL('QM2.XMITQ') USAGE(XMITQ)

Sender channel:

DEFINE CHANNEL ('QM1.QM2') CHLTYPE(SDR) DESCR('QM1 to QM2') TRPTYPE(TCP) XMITQ(QM2.XMITQ) CONNAME('localhost(1416)')

Create a queue manager alias, receiver channel to receive from QM1, transmission queue and sender channel to send message to QM3.

runmqsc QM2

Local Queue:

DEFINE QLOCAL('QM3.XMITQ') USAGE(XMITQ)

Receiver channel:

DEFINE CHANNEL ('QM1.QM2') CHLTYPE(RCVR) DESCR('QM1 to QM2')

Queue Manager Alias:

DEFINE QREMOTE ('QM3') +
       DESCR('Queue Manager alias') +
       PUT(ENABLED) +
       DEFPRTY(0) +
       DEFPSIST(YES) +
       SCOPE(QMGR) +
       RQMNAME(QM3) +
       RNAME('') +
       XMITQ(QM3.XMITQ)

Transmission queue:

DEFINE QLOCAL('QM3.XMITQ') USAGE(XMITQ)

Sender channel:

DEFINE CHANNEL ('QM2.QM3') CHLTYPE(SDR) DESCR('QM2 to QM3') TRPTYPE(TCP) XMITQ(QM3.XMITQ) CONNAME('localhost(1417)')

Create a receiver channel to receive from Q2 and a local queue.

runmqsc QM3

Local Queue:

DEFINE QLOCAL('QM3.QL')

Receiver channel:

DEFINE CHANNEL ('QM2.QM3') CHLTYPE(RCVR) DESCR('QM2 to QM3')

Advantages of Multi-hopping

Once the connectivity is established between the queue managers, you no need to create any objects at intermediate systems.
You can just create objects at source and destination queue managers and you can send message from source to destination.