MQ Tuning

Checklist - items to check in order to verify the MQ health

System Tuning

Fixes

Verify latest FixPack is applied : CSD11, Oct'2005.
AIX :

[hostmane]:/> dspmqver Name : WebSphere MQ Version : 530.6 CSD06 CMVC level : p530-06-L040211 Build type : IKAP - (Production)

LOG filesystem size

Verify there is enough space for the LOG(s) and data
AIX :

[hostmane]:/> df -k /dev/fslv00 Assigned 1.048.576 (1024-blocks) + Mounted on /logs

LOG mirroring

Make sure the LOG FileSystem is mirrored by hardware.

Backup

Verify a FileSystem BACKUP is done everytime a (important) configuration change occurs.
Use (MS03) SaveQmgrC !

MQ Tuning

Check queue manager(s), queues & channels configuration

AIX : see /var/mqm/mqs.ini

DLQ

Always define the Dead Letter Queue for any queue manager.

TxQ

The transmit queue name must match the remote queue manager name.

Put() a msg into TxQ shal trigger the Sender channel.

Applications Tuning

Message type

Use non-persistent messages whenever possible.

ALIAS

Use alias queue names to hide real configuration from applications.

Message receive buffer

There are 2 ways to MQGET() a message :

if message length is unknown, first we have to call MQGET() providing a NULL count, so we receive back the actual message length. Then we use it to allocate a buffer that is filled up with a second MQGET() call.
if max msg length is known, a fixed buffer can be pre-allocated, so only one MQGET() is required.

Run-Time Tuning

DLQ

Must be always empty

Channels

Must be always "Running"

Queues

Must be always empty

Performance can be adversely affected by:

Buffer pools that are an incorrect size
Lack of real storage
I/O contention for page sets or logs
Log buffer thresholds that are set incorrectly
Incorrect setting of the number of log buffers
Large messages
Units of recovery that last a long time, incorporating many messages for each syncpoint
Messages that remain on a queue for a long time
RACF auditing
Unnecessary security checks
Inefficient program design

System Setup Guide, page 120, 136/321.