Using parameters in Python unittest

I’ve been writing some unit tests for pymqi and fell at the first hurdle. How do I provide logon information? This cannot be hard coded because every one’s system is different. You cannot pass command line parameters to the unittest module, so how do you do it?

The second hurdle was how do I provide configuration information on what to test.
I solved these in two slightly different ways.

Logging on, or connecting to MQ

I created a separate python script called myConnect.py and put the logon information in that.

To be able to use the unit tests, you just have to customise the myConnect.py and use that.

My file does the connection, and had

import sys
import platform
import pymqi
import threading
def connect():
    queue_manager = 'CSQ9'
    qmgr = pymqi.connect(queue_manager)
    return qmgr

In my unit test script I had

import myConnect
class inq(unittest.TestCase):
    def setUp(self):
        self.qmgr = myConnect.connect()

Simple… and if I need to change my logon information, I just change one file instead of changing all of the scripts.

Passing parameters to the test.

I wanted to be able to pass a “debug option” to the tests, to be able to print information, and to pass other configuration. With the command

python3 -m unittest -v ut.inq1.test_inq_log

you cannot pass parameters.

Environment data

You can pass environment data for example, passing the variables inline

userid="user1" password="secret1" python -m unittest test

and your test.py has

user  = os.environ["userid"]
password = os.environ["password"]

External configuration file

I found it easier to set up a utparms.py and store my variables in that, for example

queues = ["CP0000","CP0001"]

I can then import and use the file.

import utparms
...
queues = utparms.queues
for q in queues:
    ....

This is different to the myConnect.py above, as the myConnect.py has logic to do the connection. The utparms.py is just a list of variable defines, with no logic.

To use this I can have a shell script like

# recreate the utmarms.py every time
cp simpleutparms.py utparms.py
python3 -m unittest -v ut.inq1.test_inq_log

cp reallybigutparms.py utparms.py
python3 -m unittest -v ut.inq1.test_inq_log

or dynamically create the utparms.py file.

Do not bang your head against a wall when you have a problem – go round it!

You may think these are obvious, but things are only obvious¹ when you understand them. Too many people write tests where the configuration information is within the test, and not isolated, so it is clearly not obvious.

¹I remember reading about a university and the definition of obvious:

If professor X says it is obvious, then it is,
If professor Y says it is obvious, then after an hours thought it should be obvious,
If professor Z says it is obvious, then after a year’s work you will understand it.

“The system resource RLIMIT_NOFILE is set at an unusually low level for IBM MQ”

I had this problem, and fixed it, and now I’ve upgraded to Ubuntu 20.04 it has come back again.

There are various hints like IBM Support telling me to change /etc/security/limits.conf, but these did not solve the problem for me.

I understand the words below, but not the overall picture. If you get this problem – and the standard changes do not work – try the /etc/systemd/user.conf change as well.

Changes to /etc/security/limits.conf apply to non GUI command windows and limits.conf is not used when systemd is running.

Recent changes to systemd include

The Linux kernel’s current default RLIMIT_NOFILE resource limit for userspace processes is set to 1024 (soft) and 4096 (hard). Previously, systemd passed this on unmodified to all processes it forked off. With this systemd release the hard limit systemd passes on is increased to 512K, overriding the kernel’s defaults and substantially increasing the number of simultaneous file descriptors unprivileged userspace processes can allocate …

For graphical login. command windows (such as GNOME on Linux) you need.. (I’m copying)

Add the following line to /etc/systemd/user.conf:

DefaultLimitNOFILE=65535

That change works, but only affecting the soft limit. (Leaving us capped with a hard limit of 4096 still.) In order to affect the hard limit, we must modify /etc/systemd/system.conf with the same changes.

Hell is PCF.

In Dante’s book “Inferno”, the gates of hell have “Abandon all hope, ye who enter here” inscribed upon them. The book describes Dante’s journey to the deepest levels of hell.

I had a similar journey, not so far, trying to use PCFs in common code.

I thought I knew how to use MQ PCFs to display and extract information about MQ and its objects, but “fools rush in where angels fear to tread”.

Thanks to Morag Hugson of MQGEM for her help in getting me through this journey.

The kindergarten course on using PCF

Do not use PCF, use the display commands and parse the output. Parsing the output is a simpler problem to solve than trying to use PCF.

The high school course.

Instead of using a command DIS Q(…) you use PCF; create a message with a series of control blocks, send the request to a system queue, and get the data back in a similar format.

There is a header control block to define the function, and 0 or more control blocks each of which define a field.

The first control block, the header block, defines the request. It has an integer request field, such as MQCMD_INQUIRE_Q.
The second and following control blocks are field control blocks, they have
- A field to define the type of data, for example character string, byte string (may contain hex 00s), integer, 64 bit integer, or arrays of data.
- A field to define which field is defined, for example the integer MQCA_Q_NAME
- For strings and byte strings, the length of the data.
- For strings the code page of the data.
- The data.

The request is put to a system queue and the response comes back in the reply_to queue you specified. This has a similar format as the request:

There is a header giving the request type, (MQCMD_INQUIRE_Q), the condition and reason code, and a count of the fields returned.
There are 0 or more field control blocks – the same as above.

Your program can chain down the field control blocks and can display the fields.

The program from the first year high school will report data like

field type 20 has value 1

which is not very usable.

Using the supplied header file CMQSTRC, you can call MQIA_STR(20) and get back “MQIA_Q_TYPE”. So now you know this field is the Queue Type data.

Now you know it is a Q_Type you can use the function MQQT_STR(1) and get back the string “MQQT_LOCAL”. You can determine the queue type value as a string using

if (field_type=MQIA_Q_TYPE ) 
    queue_type= MQQT_STR(value)
else if (field_type=MQIACF_PUBSUB_PROPERTIES,)                
    property_type=MQPSPROP_STR(value)
else if (field_type...)

You need a bit of code to match up the field type to the routing you need to call to get the data back. I am working on a function getValue(20,0) to get back “MQIA_Q_TYPE”, and “MQQT_LOCAL”. One call which returns, the data type and its character representation of the value, which will make life much easier for the programmer. There are over 200 field types and it is hard to find the mapping for the value.

In early days of MQ there were two choices of header. You issued a header with type MQCFT_COMMAND and got back one reply with a header type MQCFT_RESPONSE, and all of the data.

Not too difficult so far.

Going down to the next level of hell with z/OS. The request “inquire_chinit” goes to the command server, which sends back “Request received”. The command server then sends the request to the chinit, which sends the response back to the command server, which sends it on to your reply to queue.

You now have to manage at least two reply messages, one for the “Request received”, and one or more for the data.

The next complication which takes you down to the next level of hell, is Shared Queue on z/OS.

You can issue the PCF request saying “hello all queue managers, please give me information about the queue status as you see it for queue COLINPAICEQ”. This request can now go to multiple queue managers, and you get multiple replies back which you have to manage.

This is not well documented in the official documentation. It jumps straight to the PhD class.

I’ll try to explain the data you get back with some examples.

Example 1 Inquire queue manager.

I sent the PCF request with MQCMD_INQUIRE_Q_MGR.

Two messages were returned. They had the same msgid and correlid

The first message was type MQCFT_XR_ITEM with sequence number 1, the second message was MQCFT_XR_SUMMARY with sequence number 2.

First message

Header

Type MQCFT_XR_ITEM: Message is an extended response to an Inquire command. It contains item data.
Command Request MQCMD_INQUIRE_Q_MGR
Condition code 0
Reason code 0
Sequence number 1
It is not last message in set.
Parameter count 107

Data fields

MQBACF_RESPONSE_ID … a 24 character string with hexadecimal values. Think of this as a correlator field, so you can match all the responses for this request.
MQCACF_RESPONSE_Q_MGR_NAME : ‘CSQ9’. This is the queue manager which sent the response.
MQCA_Q_MGR_NAME : ‘CSQ9’
MQCA_Q_MGR_DESC : ‘CSQ9, IBM MQ for z/OS – V9.0.1’
MQIA_PLATFORM : MQPL_ZOS
MQIA_CPI_LEVEL : 100
MQIA_COMMAND_LEVEL : MQCMDL_LEVEL_924
…

Second message

Header

Type: MQCFT_XR_SUMMARY . Message is an extended response to a command. It contains summary information.
Request INQ_QMGR
Condition code 0
Reason code 0
Sequence number 2
It is the last message in set.
Number of parameters 2

MQBACF_RESPONSE_ID: …. same as above.
MQCACF_RESPONSE_Q_MGR_NAME: ‘CSQ9’

These two fields are used to correlate requests. I think …XR_SUMMARY really means end of messages in this set.

Example 2 Inquire chinit.

I sent the PCF request with MQCMD_INQUIRE_CHANNEL_INIT.

Five messages were returned. They all had the same msgid and correlid

The first response message was type MQCFT_XR_MSG with sequence number 1.

The the remaining four messages were part of one set. They had

Queue manager information, such as number of dispatchers.
Information about the TCP/IP listener
Information about the LU 62 listener
The “end” or summary record

First set, single message

Header

Type 17 MQCFT_XR_MSG: Message is an extended response to a command. It contains informational or error details.
Command MQCMD_INQUIRE_CHANNEL_INIT
Condition code 0
Reason code 0
Sequence number 1
It is the last message in set.
4 field control blocks were returned.

Field control blocks

MQBACF_RESPONSE_ID: Value: 24 bytes of data (with the queue manager name in it
MQCACF_RESPONSE_Q_MGR_NAME: 48 character queue manager name
MQIACF_COMMAND_INFO : MQCMDI_COMMAND_ACCEPTED
MQBACF_RESPONSE_SET: Same value as the first field control block

Set 2, first message

Header

Type: MQCFT_XR_ITEM: Message is an extended response to an Inquire command. It contains item data.
Request Command MQCMD_INQUIRE_CHANNEL_INIT
Reason code 0
Sequence number 1
It is not the last message in set.
Parameter count 20.

Field control blocks – information about the chinit

MQBACF_RESPONSE_ID: Value: 24 bytes of data (with the queue manager name in it)
MQCACF_RESPONSE_Q_MGR_NAME: 48 character queue manager name
MQIACF_CHINIT_STATUS : MQSVC_STATUS_RUNNING
MQIACH_ADAPS_STARTED : 8
MQIACH_ADAPS_MAX :8
MQIACH_DISPS_STARTED :5
MQIACH_DISPS_MAX :5
…

Set 2, second message

Header

Type: MQCFT_XR_ITEM Message is an extended response to an Inquire command. It contains item data.
Request Command MQCMD_INQUIRE_CHANNEL_INIT
Reason code 0
Sequence number 2
It is not the last message in set.
Parameter count 7.

Field control blocks – status of TCP listener

MQBACF_RESPONSE_ID …
MQCACF_RESPONSE_Q_MGR_NAME : b’CSQ9′
MQIACH_LISTENER_STATUS : MQSVC_STATUS_RUNNING
MQIACH_XMIT_PROTOCOL_TYPE : MQXPT_TCP
MQIACH_INBOUND_DISP: MQINBD_Q_MGR
MQIACH_PORT_NUMBER :1414
MQCACH_IP_ADDRESS : b’*’

Set 2, third message

Header

Type: MQCFT_XR_ITEM Message is an extended response to an Inquire command. It contains item data.
Request Command MQCMD_INQUIRE_CHANNEL_INIT
Reason code 0
Sequence number 2
It is not the last message in set
Parameter count 5.

Field control blocks – status of LU62 listener

MQBACF_RESPONSE_ID ….
MQCACF_RESPONSE_Q_MGR_NAME : b’CSQ9′
MQIACH_LISTENER_STATUS : MQSVC_STATUS_STOPPED
MQIACH_XMIT_PROTOCOL_TYPE : MQXPT_LU62
MQIACH_INBOUND_DISP MQINBD_Q_MGR

Set 2, fourth (and last) message

Header

Type: 18 MQCFT_XR_SUMMARY Message is an extended response to a command. It contains summary information.
Request Command MQCMD_INQUIRE_CHANNEL_INIT
Reason code 0
Sequence number 4
It is the last message in set.
Parameter count 2.

Field control blocks

MQBACF_RESPONSE_ID …
MQCACF_RESPONSE_Q_MGR_NAME : ‘CSQ9’

I do not have access to a QSG, so cannot document the records for a QSG wide query.

Creating the data fields

If you want to create a PCF command to change a queue, you need the PCF header to describe the command, and data fields to identify the queue, and changed attributes.

The header is defined with control block MQCFH (not MQPCFH, I keep trying to use). There are several fields, the key one is Command. In this case we need MQCMD_CHANGE_Q. All request begin with MQCMD. There is MQCMD_INQUIRE_Q for displaying information about a queue.

There is a good post on PCF fields, called Morag’s Quirk’s #14: MQCFH Versions which contains some good information on data types and their usage.

There is a variety of data field record types, such as Byte string, Character string, Integer; and different usages

The field can be

passed with the command, (a selector), and returned. For example MQIA_, MQCA_
returned (but not passed through with a command); for queue manager for example MQCACF, and MQIACF) and for the CHINIT for example (MQCACH and MQIACH)

or to look at it a different way…

MQIA_ are the set used on MQINQ – and thus defined in cmqc.h. They can also be used in PCF rather than defining a second ID for the same parameter.
MQIACF_ are the set used solely for PCF – and thus defined in cmqcfc.h. They are not used on MQINQ.
MQIACH_ are the set used for channel commands, they are defined in cmqcfc.h.

The same logic is for for MQCA_/MQCACF_/MQCACH_.

Each field has a unique number, and the field types are generally grouped within a range, but not all of them. The monitoring integers and 64 bit integers are all mixed up.

To find the string representation of the unique number you can call the formatting functions (*MQBACF_STR, *MQCA_STR, *MQCACF_STR, *MQCACH_STR, *MQIA_STR, *MQIACF_STR, *MQIACH_STR, *MQIAMO_STR, *MQIAMO64_STR) in CMQSTRC.h. These routines return a string matching the number or the empty string ”. I found I have to go through them each in turn until there is a match.

In more detail.

Individual fields
- A byte string (MQCFBS) . This is a string which can include hexadecimal characters, such as a message id or correlid. It does not get converted to a different code page. There are fields
  - MQBACF_ (Byte Parameter Types ) and are in the range 7001 to 7039.
- A character string(MQCFST). This is a string such as queue name. This has a code page associated with it. This allows you to convert from ASCII to EBCDIC (or other conversion). There are fields
  - MQCA_ (Character Attribute Selectors) and are in the range 2001 to 2999 range (and 4000) for queue manager values .
  - MQCACF_ (Character Queue Manager Parameter Types) in the range 3000 to 3211 + a couple in the 55xx range.
  - MQCACH_ (Character Channel Parameter Types) in the range 3500 to 3573
- An integer (MQCFIN), such as queue depth, or the value to mean “Enabled” or “Disabled”. There are fields
  - MQIA_, (Integer Attribute Selectors) integers in the range of 1 to 275 ( and 2000).
  - MQIACF_, (Integer Queue Manager Parameter Types) and are number in the range of 1 to 1440.
  - MQIACH_, (Integer Channel Types) and in the range 1501 to 1646.
- A 64 bit integer(MQCFIN64). For example MQIAMO64_GET_BYTES, the number of bytes got as a integer 64 number. The values are intermixed with MQIAMO_ numbers. These are only used by the monitoring code – there are no MQIA*64 for anything else
Lists of fields
- 64 bit integers(MQCFIL64). These are used in the midrange monitoring
- integers(MQCFIL)
- character strings(MQCFSL)
A group of (sub) parameters (MQCFGRP).
- For example with application activity. This has a several groups. One of these groups is “Operations” which contains a set of PCF data for Operation type, Operation time, QMGR name).
- They are also used in command events – but not used in command server messages.
- These have a type field of MQGACF_ and are in the range 8001 to 9000
Filters – which provides the same function as the “WHERE” clause on a command.
- Passing in a byte string (MQCFBF),
- Passing a string (MQCFSF)
- Passing in an integer string(MQCFIF).

Using PCF

It takes a while to understand how to use PCF. I found I had to write a lot of code to handle the PCF data and covert from numeric values to useful character strings so as to produce useful output. It does all work – it is just hard to get it to work.
To make it just a touch more complex, you may need to worry about data conversion and strings having different length when doing conversion, but I’ll leave this “as an exercise for the reader”¹.

(¹)Quote: The phrase is sometimes used as a joke. When a writer gets to the difficult part of a problem and he doesn’t want to take the trouble to solve it, or doesn’t know how to solve, he says this is “left as an exercise for the reader”, as if it was too trivial to waste space in the book discussing, when really the issue is that he can’t figure out the answer himself.

Problems with Firefox accessing sites?

I was having problems accessing the IBM documentation from my Firefox browser. Nothing was displayed. The Firefox error log reported problems with some of the HTML. I started getting problems with other sites, such as being unable to logon to gmail. I was getting annoyed with all of these little problems, so I decided to find out why.

I eventually fixed the problems by refreshing Firefox. Type about:support on the input line, and click the box saying “Refresh Firefox”. After a few moments it came back and worked.

I can access all sites, including the IBM documentation.

I only regret clearing my cache beforehand!

Help! I’m in a Dilbertian, looking-glass world

I’ve spent an hour struggling with a web site trying to download some files and was amazed at the poor usability of the web site. I tried an alternate supplier, and this was just as bad.

It feels like I am in a world which is upside down, and what is obvious to me, is clearly not obvious to other people who ~~design~~ build these web sites.

I was talking to someone who lives in an “architect designed house” which looks very smart, but is not very practical. There is an open plan kitchen, flowing into the seating area, and upstairs to the open plan master bedroom. When smelly food is being cooked, you smell it in the lounge and in the master bedroom ; just imagine waking up the the smell of last night’s curry. The master bedroom has very little privacy. The master bedroom has a bath in it, with views over the town and hills. Your bedroom will be full of damp air! An “architect designed” does not mean practical and useful. Perhaps the same architect also builds web sites.

The design brainstorm

I can visualise the conference room where Dilbert’s Pointy Haired Boss is telling the team about the goals of the new web site for ordering CDs

“A good measure of a web site, is how much time people spend on it. I hear people spend all day on Facebook and that is popular”
“Real estate is valuable – so use as much as you can”
Use the latest Java Script tools to make it look really modern; Can we display lines where nothing is displayed until you move your mouse over it? That would be really cool.

Marketing terms

“These are the “upside down” terms we will use in our Marketing material – please ensure you follow them”

“Improved” : worse;slower
“Intuitive”: When you’ve used the interface for a few weeks, you know how your way around, and know the pitfalls.
“Elegant”: we use the design for a mobile phone on a web page, so the users have a narrow column of data, and do not use the available space in the web browser.
“Modern”: more (or less) rounded corners; different fonts (which make it harder to read – do not use the fonts which dyslexics find easier to read).
“Uncluttered”: provide less information on the screen; remove visual clues.
“Dynamic”: we use a lot of interactive scripts which look cool; such as windows that disappear when you move your mouse over them.
“Smart icons”: for example FEEDback is about FEEDing which is about food – so use a knife and fork for the icon – clever idea isn’t it?.

A Jelly Bean for the person who can use the greatest number of these terms.

The outcome

Allow search for some topics, such as Pop group – but not the name of the CD.
Use lots of space on the web page. For example we could easily display 40 items on a page – let’s display just 10 and make them ask for the next page by a “more”button. Though having just one line per screen would be silly – wouldn’t it?
List information like “Beatles hits by year” – but not the name of the CD. You have to select on each line to see what the CD is.
When they click to see what is in each CD, do not display all of the contents, just display 3 entries “inline” and give them another “more button”
When you click on a line you can select “Buy”. When they use the browser back button – do not go back to where they came from, go to the start of the web site, and so more clicks on our site. They stay logged on – it would be stupid to make them logon every time wouldn’t it?
Make the site inconsistent. Sometimes you can click on a line for more information, sometime you have to click on the button at the end of the line – that only appears when you hover over it.
Have buttons on the page which have no description or hover text, until you have clicked on it. For example ‘contact us’.
Use really big fonts to use more space.
Can we sell a course on how to use our interface? If people who have never used our web site before can quickly order things this counts as a failure because they didn’t spend much time on the web site.
Make it slow – so people spend more time on the site – but provide some good animation (such as a greyhound racing) to make people think it is doing something useful.

Back in the real world.

I remember having a talk about 20 years ago by a UI expert. I cannot remember all of it, but the points I remember were….

Make it easy for the end user
1. Minimise the actions the user has to take (clicks, scrolls etc). Put the “up arrow” adjacent to the “down arrow”- not at different ends of the screen. If they have to keep clicking a button – put the buttons close to the same place on each page.
2. Make actions obvious
3. If the web site is slow, and you have to keep doing “next” this will frustrate the user. Is it better to have one page to load slowly with all of the information – or have smaller pages which take seconds to load?
4. Test it in a typical environment. I remember trying to use the IBM documentation web site from a customer using a dial up in Indonesia, going to the UK, to go to the US. IBM support said the response time was “ok” because they were in the same building as the server! For me it was taking me minutes per page.
5. Creating a dyslexia friendly workplace is a very useful site.
Make the best use of available space
1. Use the appropriate font. For one page – do you need a big font? No. For a 50 “page” you need bigger fonts to make the sections visible.
2. Try to provide the most information on the screen as possible – without going too far. For a list of items consider colouring every 3rd or 5th line to help the user keep their eye on the line.
3. Make all information visible – do not hide it. Do not make users move the mouse over something to display it.
4. If you have icons, make sure the icons are “standard”.
5. Consider how much you display before having a “more” button. If you expect people to “find” data, then have more lines, and make it scrollable. Too much data ( > 1000 lines) can make it slow to load. I think 100 -200 lines is acceptable.
6. Provide information the end user wants. If all the items in a list are for “ABC Wonderful software product for new users”.
  - This would be clearer
    - ABC Wonderful software product for new users English edition
    1. version 1
    2. version 2
    3. version 3
  - than
    1. ABC Wonderful software product for new users V1English edition
    2. ABC Wonderful software product for new users V2 English edition
    3. ABC Wonderful software product for new users v3 English edition.

Make it clear what each part is, for example a link (it is underlined). it should be obvious from looking at it – the end user should not have to move the mouse to display it. ( I know modern “standards” seem to say do not underline a link – let the end user guess). Consider people with screen readers and how they read and navigate it.
Less is more. I know of this from my acting. A character who is still, with small moves, is often more powerful than big gestures. People expect a web site with response time of around 1-2 seconds. The BBC new web site https://www.bbc.co.uk/news/uk displays for me in under 2 seconds ( usually 1 second) with full graphics. Some sites I use frequently take over 5 seconds, sometimes 10 seconds. Do we really need clever animation etc.?
The word “Intuitive” is often abused.
1. If you use windows 10 as your primary work station then move to windows 11; the GUI is the same as before. You find it “intuitive”. I come from Linux, and having to use Windows, a lot is not intuitive. Similarly someone going from Windows to Linux will not find it entirely intuitive. You have to allow for people who are not familiar with the web site as well as people who use frequently use the web site (eg the web site developer and testers).
2. Icons are often not obvious. Giving them useful information via a hover is a good start.
When testing usability of web pages, use people who have never used your site before. The worst people for testing the new user experience, are those who use it every day and who work round the problems.

What was new in the MQ API?

I wanted to know what new features were available in different releases of MQ, but could not find the information documented.

I’ve taken the CMQC C header file from different releases on z/OS and shown the differences!

MQ V8.0 to V9.0.1
- CMQC
- CMQCFC
MQ V9.0.1 to V9.1.1
- CMQC
- CMQCFC
MQ 9.1.1 to MQ 9.2.2
- CMQC
- CMQCFC
MQ 9.2.2 to MQ 9.2.4
- CMQC
- QMQCFC

From MQ V8.0 to V9.0.1

CMQC

MQCNO_CURRENT_VERSION          5      
MQCNO_VERSION_6                6 
MQCNO_CURRENT_VERSION          6

MQCNO_CURRENT_LENGTH           188    
MQCNO_LENGTH_6                 208 
MQCNO_CURRENT_LENGTH           208 

MQAT_MCAST_PUBLISH             36 
MQAT_AMQP                      37 
MQAT_DEFAULT                   2 

MQOT_PROT_POLICY               1019 
MQOT_TT_CHANNEL                1020 
MQOT_AMQP_CHANNEL              1021 
MQOT_AUTH_REC                  1022 
MQ_AMQP_CLIENT_ID_LENGTH       256
MQRC_STORAGE_MEDIUM_FULL       2192
MQRC_ADMIN_TOPIC_STRING_ERROR  2598 
MQRC_AMQP_NOT_AVAILABLE        2599 
MQRC_CCDT_URL_ERROR            2600
MQADOPT_CHECK_CHANNEL_NAME     8  

MQCMDL_CURRENT_LEVEL           800                         
MQCMDL_LEVEL_801               801 
MQCMDL_LEVEL_802               802 
MQCMDL_LEVEL_900               900 
MQCMDL_LEVEL_901               901 
MQCMDL_LEVEL_902               902 
MQCMDL_LEVEL_903               903 
MQCMDL_LEVEL_904               904 
MQCMDL_LEVEL_905               905 
MQCMDL_CURRENT_LEVEL           905 

MQPL_APPLIANCE                 28
MQCAP_EXPIRED                  2 

 /* Media Image Scheduling */ 
MQMEDIMGSCHED_MANUAL           0 
MQMEDIMGSCHED_AUTO             1 
                                                                 
 /* Automatic Media Image Interval */ 
MQMEDIMGINTVL_OFF              0 
                                                                 
 /* Automatic Media Image Log Length */ 
MQMEDIMGLOGLN_OFF              0 
                                                                 
 /* Media Image Recoverability */ 
MQIMGRCOV_NO                   0 
MQIMGRCOV_YES                  1 
MQIMGRCOV_AS_Q_MGR             2

MQCA_AMQP_SSL_CIPHER_SUITES    2137 
MQCA_AMQP_VERSION              2136  
  
MQCA_LAST_USED                 2135     
MQCA_LAST_USED                 2137   

MQIA_ADVANCED_CAPABILITY       273 
MQIA_AMQP_CAPABILITY           265 

MQIA_AUTHENTICATION_METHOD     266
MQIA_KEY_REUSE_COUNT           267 

MQIA_LAST_USED                 264               
MQIA_LAST_USED                 273   

/* Key reuse count */ 
MQKEY_REUSE_DISABLED           0 
MQKEY_REUSE_UNLIMITED          (-1)  

struct tagMQCNO { 
  ...
  PMQCHAR    CCDTUrlPtr;           /* Address of CCDT URL string */ 
MQLONG     CCDTUrlOffset;        /* Offset of CCDT URL string */ 
MQLONG     CCDTUrlLength;        /* Length of CCDT URL */ 
MQBYTE8    Reserved;             /* Reserved */ 
  /* Ver:6 */  
}
...
MQCNO_DEFAULT ....

CMQCFC

MQCMD_INQUIRE_AMQP_CAPABILITY  216 
MQCMD_AMQP_DIAGNOSTICS         217

MQRCCF_CLWL_EXIT_NAME_ERROR    3374 
MQRCCF_SERVICE_NAME_ERROR      3375 
MQRCCF_REMOTE_CHL_TYPE_ERROR   3376 
MQRCCF_TOPIC_RESTRICTED        3377 
MQRCCF_CURRENT_LOG_EXTENT      3378 
MQRCCF_LOG_EXTENT_NOT_FOUND    3379 
MQRCCF_LOG_NOT_REDUCED         3380 
MQRCCF_LOG_EXTENT_ERROR        3381 
MQRCCF_ACCESS_BLOCKED          3382 

MQ_ENTITY_NAME_LENGTH          64             
MQ_ENTITY_NAME_LENGTH          1024  


MQIAMO_MONITOR_CLASS           839 
MQIAMO_MONITOR_TYPE            840 
MQIAMO_MONITOR_ELEMENT         841 
MQIAMO_MONITOR_DATATYPE        842 
MQIAMO_MONITOR_FLAGS           843 
MQIAMO64_QMGR_OP_DURATION      844 
MQIAMO64_MONITOR_INTERVAL      845 
MQIAMO_LAST_USED               845 

/* Defined values for MQIAMO_MONITOR_FLAGS */ 
MQIAMO_MONITOR_FLAGS_NONE      0 
MQIAMO_MONITOR_FLAGS_OBJNAME   1 
                                                       
/* Defined values for MQIAMO_MONITOR_DATATYPE */ 
MQIAMO_MONITOR_UNIT            1 
MQIAMO_MONITOR_DELTA           2 
MQIAMO_MONITOR_HUNDREDTHS      100 
MQIAMO_MONITOR_KB              1024 
MQIAMO_MONITOR_PERCENT         10000 
MQIAMO_MONITOR_MICROSEC        1000000 
MQIAMO_MONITOR_MB              1048576 
MQIAMO_MONITOR_GB              100000000 

MQIACF_AMQP_ATTRS              1401 
MQIACF_AMQP_DIAGNOSTICS_TYPE   1406 

MQIACF_SYSP_MAX_CONC_OFFLOADS  1412          
MQIACF_LAST_USED               1412          
MQIACF_AUTH_REC_TYPE           1412 
MQIACF_SYSP_MAX_CONC_OFFLOADS  1413 
MQIACF_SYSP_ZHYPERWRITE        1414 
MQIACF_Q_MGR_STATUS_LOG        1415 
MQIACF_ARCHIVE_LOG_SIZE        1416 
MQIACF_MEDIA_LOG_SIZE          1417 
MQIACF_RESTART_LOG_SIZE        1418 
MQIACF_REUSABLE_LOG_SIZE       1419 
MQIACF_LOG_IN_USE              1420 
MQIACF_LOG_UTILIZATION         1421 
MQIACF_LOG_REDUCTION           1422 
MQIACF_LAST_USED               1422 

MQIACH_LAST_USED               1643  
MQIACH_AMQP_KEEP_ALIVE         1644 
MQIACH_SECURITY_PROTOCOL       1645 
MQIACH_LAST_USED               1645

MQCAMO_LAST_USED               2712  
MQCAMO_MONITOR_CLASS           2713 
MQCAMO_MONITOR_TYPE            2714 
MQCAMO_MONITOR_DESC            2715 
MQCAMO_LAST_USED               2715 
                                             
MQCACF_LAST_USED               3206  
MQCACF_AMQP_CLIENT_ID          3207 
MQCACF_ARCHIVE_LOG_EXTENT_NAME 3208 
MQCACF_LAST_USED               3208 

MQCACH_LAST_USED               3570  
MQCACH_TOPIC_ROOT              3571 
MQCACH_LAST_USED               3571

MQGACF_LAST_USED               8014
MQGACF_MONITOR_CLASS           8015 
MQGACF_MONITOR_TYPE            8016 
MQGACF_MONITOR_ELEMENT         8017 
MQGACF_LAST_USED               8017 
  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -
MQACT_REDUCE_LOG               10 
MQACT_ARCHIVE_LOG              11 
                                             

MQEVO_REST                     8 

MQRQ_FAILOVER_PERMITTED        30 
MQRQ_FAILOVER_NOT_PERMITTED    31 
MQRQ_STANDBY_ACTIVATED         32 

MQLDAP_AUTHORMD_SRCHGRPSN      3 

/* Authentication Method */ 
MQAUTHENTICATE_OS              0 
MQAUTHENTICATE_PAM             1 
                                                
/* Reduce Log Options */ 
MQLR_ONE                       1 
MQLR_AUTO                      (-1) 
MQLR_MAX                       (-2)

From MQ 9.0.1 to MQ 9.1.1

CMQC

MQCNO_CURRENT_VERSION          6          
MQCNO_VERSION_7                7 
MQCNO_CURRENT_VERSION          7 
 
MQCNO_CURRENT_LENGTH           208            
MQCNO_LENGTH_7                 240 
MQCNO_CURRENT_LENGTH           240 

MQCNO_GENERATE_CONN_TAG        0x00200000

MQAN_NONE 
MQAN_NONE_ARRAY
MQRC_INCOMPLETE_TRANSACTION    2147  
MQRC_Q_MGR_RECONNECT_REQUESTED 2601
MQRC_SUB_JOIN_NOT_ALTERABLE    29440

/* Max queue file size values */ 
MQQFS_DEFAULT                  (-1) 

MQCMDL_CURRENT_LEVEL           905               
MQCMDL_LEVEL_910               910 
MQCMDL_LEVEL_911               911 
MQCMDL_LEVEL_912               912 
MQCMDL_LEVEL_913               913 
MQCMDL_LEVEL_914               914 
MQCMDL_LEVEL_915               915 
MQCMDL_CURRENT_LEVEL           915 

MQIA_LAST_USED                 273          
MQIA_LAST_USED                 274   

MQIA_MAX_Q_FILE_SIZE           274  

struct tagMQCNO { 
  ...   
  MQCHAR28   ApplName;             /* Application name */ 
  MQBYTE4    Reserved2;            /* Reserved */ 
  /* Ver:7 */ 
};
MQCNO_DEFAULT....

CMQCFC

 MQCMD_AMQP_DIAGNOSTICS         217 
 MQCMD_INTER_Q_MGR_STATUS       218 
 MQCMD_INTER_Q_MGR_BALANCE      219 
 MQCMD_INQUIRE_APPL_STATUS      220 

 MQRCCF_PS_REQUIRED_MQUC        3383 
 MQRCCF_OBJECT_ALREADY_EXISTS   4001 

 MQRCCF_APPL_STATUS_NOT_FOUND   4097 
 MQCFT_STATUS                   27 

MQBACF_LAST_USED               7035   
MQBACF_REQUEST_ID              7036 
MQBACF_PROPERTIES_DATA         7037 
MQBACF_CONN_TAG                7038 
MQBACF_LAST_USED               7038 

MQIACF_LAST_USED               1422   
MQIACF_IGNORE_STATE            1423 
MQIACF_MOVABLE_APPL_COUNT      1424 
MQIACF_APPL_INFO_ATTRS         1425 
MQIACF_APPL_MOVABLE            1426 
MQIACF_REMOTE_QMGR_ACTIVE      1427 
MQIACF_APPL_INFO_TYPE          1428 
MQIACF_APPL_INFO_APPL          1429 
MQIACF_APPL_INFO_QMGR          1430 
MQIACF_APPL_INFO_LOCAL         1431 
MQIACF_APPL_IMMOVABLE_COUNT    1432 
MQIACF_BALANCED                1433 
MQIACF_BALSTATE                1434 
MQIACF_APPL_IMMOVABLE_REASON   1435 
MQIACF_DS_ENCRYPTED            1436 
MQIACF_CUR_Q_FILE_SIZE         1437 
MQIACF_CUR_MAX_FILE_SIZE       1438 
MQIACF_LAST_USED               1438 

MQIACH_LAST_USED               1645         
MQIACH_SPL_PROTECTION          1646 
MQIACH_LAST_USED               1646 

MQCACF_LAST_USED               3208         
MQCACF_APPL_IMMOVABLE_DATE     3209 
MQCACF_APPL_IMMOVABLE_TIME     3210 
MQCACF_LAST_USED               3210 

MQGACF_LAST_USED               8017         
MQGACF_APPL_STATUS             8018 
MQGACF_CHANGED_APPLS           8019 
MQGACF_ALL_APPLS               8020 
MQGACF_APPL_BALANCE            8021 
MQGACF_LAST_USED               8021 
                                            
MQIS_NO                        0 
MQIS_YES                       1 

/* Movable Options */ 
MQAPPL_IMMOVABLE               0 
MQAPPL_MOVABLE                 1 
                                    
/* Active Options */ 
MQACTIVE_NO                    0 
MQACTIVE_YES                   1 
                                    
/* Balance Options */ 
MQBALANCED_NO                  0 
MQBALANCED_YES                 1 
MQBALANCED_NOT_APPLICABLE      2 
MQBALANCED_UNKNOWN             3 
                                    
/* Balance State */ 
MQBALSTATE_NOT_APPLICABLE      0 
MQBALSTATE_LOW                 1 
MQBALSTATE_OK                  2 
MQBALSTATE_HIGH                3 
MQBALSTATE_UNKNOWN             4 

  /* Immovable Reasons */ 
MQIMMREASON_NONE               0 
MQIMMREASON_NOT_CLIENT         1 
MQIMMREASON_NOT_RECONNECTABLE  2 
MQIMMREASON_MOVING             3 
MQIMMREASON_APPLNAME_CHANGED   4

From MQ 9.1.1 to MQ 9.2.2

CMQC

MQ_NHA_INSTANCE_NAME_LENGTH    48 

MQCMDL_CURRENT_LEVEL           915    
MQCMDL_LEVEL_920               920 
MQCMDL_LEVEL_921               921 
MQCMDL_LEVEL_922               922 
MQCMDL_CURRENT_LEVEL           922

CMQCF

MQCACF_APPL_IMMOVABLE_TIME     3210 
MQCACF_LAST_USED               3210       
MQCACF_NHA_INSTANCE_NAME       3211 
MQCACF_LAST_USED               3211

MQRQ_STANDBY_ACTIVATED         32 
MQRQ_REPLICA_ACTIVATED         33

From MQ 9.2.2. to 9.2.4

CMQC

MQBNO structure and  MQBNO_ constants

MQCNO_CURRENT_VERSION          7
MQCNO_VERSION_8                8 
MQCNO_CURRENT_VERSION          8

MQCNO_CURRENT_LENGTH           240    
MQCNO_LENGTH_8                 252 
MQCNO_CURRENT_LENGTH           252 

MQ_TEMPORARY_Q_PREFIX_LENGTH   32 
MQRC_BNO_ERROR                 2602 
MQRC_OUTBOUND_SNI_NOT_VALID    2603 

/* Streaming Queue Quality of Service Values */ 
MQST_BEST_EFFORT               0 
MQST_MUST_DUP                  1 

MQCMDL_CURRENT_LEVEL           922       
MQCMDL_LEVEL_923               923 
MQCMDL_LEVEL_924               924 
MQCMDL_CURRENT_LEVEL           924 

MQCA_LAST_USED                 2137
MQCA_LAST_USED                 2138 

MQIA_LAST_USED                 274      
MQIA_LAST_USED                 275 

MQIA_STREAM_QUEUE_QOS          275 

struct tagMQCNO { 
   ...     
   PMQBNO     BalanceParmsPtr;      /* Balance Parameter Pointer */ 
   MQLONG     BalanceParmsOffset;   /* Balance Parameter Offset */ 
   MQBYTE4    Reserved3;            /* Reserved */ 
   /* Ver:8 */ 
 };

CMQCFC

MQRCCF_STREAMQ_DEST_NOT_SUPP   3384 
MQRCCF_STREAMQ_DEST_CONFLICT   3385 
MQRCCF_STREAMQ_NOT_SUPPORTED   3386 
MQRCCF_STREAMQ_CONFLICT        3387 
 
MQBACF_LAST_USED               7038    
MQBACF_MQBNO_STRUCT            7039 
MQBACF_LAST_USED               7039 
  
MQIACF_SYSP_SMF_STAT_TIME_MINS 1199 
MQIACF_SYSP_TRACE_CLASS        1200 
  
MQIACF_LAST_USED               1438
MQIACF_BALANCING_TYPE          1439 
MQIACF_BALANCING_OPTIONS       1440 
MQIACF_BALANCING_TIMEOUT       1441 
MQIACF_SYSP_SMF_STAT_TIME_SECS 1442 
MQIACF_SYSP_SMF_ACCT_TIME_MINS 1443 
MQIACF_SYSP_SMF_ACCT_TIME_SECS 1444 
MQIACF_LAST_USED               1444 

MQIACH_AUTH_INFO_TYPES         1622 

MQCACH_LAST_USED               3571      
MQCACH_TEMPORARY_MODEL_Q       3572 
MQCACH_TEMPORARY_Q_PREFIX      3573 
MQCACH_LAST_USED               3573 
                                         
MQIMMREASON_APPLNAME_CHANGED   4 
MQIMMREASON_IN_TRANSACTION     5 
MQIMMREASON_AWAITS_REPLY       6

“I do not understand these get counts on z/OS”

I had a question from someone who was trying to use the MQ SMF statistics to understand their queue manager usage. This came from a post from Lynn Elkins who was talking about “Data ManagerGets”. I started writing a short answer… but the answer got longer, so I thought I would post on this topic.

The z/OS queue manager has different components, for example the logging component which manages recovery data, the buffer manager which manages pages in the buffer pool, the message manager which handles the API side of MQ requests, and the data manager which manages who messages are mapped to pages in a page set.

There is an SMF statistic QMSTGET which is the number of application MQGET requests, and QISTMGET, the number of requests to data manager to start getting a messages.

I’ll give some examples and explain why there could be a big difference in the numbers.

Shared queue

Simple MQGET of shared queue

An application issues an MQGET, there is a message on the queue but this is a shared queue, so data manager is not involved

QMSTGET is now +1, QISTMGET is unchanged

Local queue

Simple MQGET of local queue

An application issues an MQGET, there is a message on the queue the messsage is returned.

QMSTGET is now +1, QISTMGET is +1GET.

Get with wait when there was no message on the queue

The application issues an MQGET, so increment QMSTGET. The queue is empty, so do not change QISTMGET. Control is returned to the adapter and the application waits. A message arrives, the application is woken up, and reissues the MQGET. The message is returned.

Increment QMSTGET again, increment QISTMGET.
QMSTGET is now +2, QISTMGET is +1

The getting application polls the queue

Rather than use MQGET with wait, the application issues MQGET with no wait. There is a code

Loop forever:
MQGET; if message available then leave loop
else wait for 1 second
end

After 1 hour the statistics could be

QMSTGET is now + 3600, QISTMGET is unchanged.

Multiple applications waiting on a queue

100 applications issue MQGET with wait on a queue.
- QMSTGET is now +100, and all applications are waiting in the adapter.
A message arrives one application wakes up and gets the message
- QMSTMGET is now +101, QISTGET is now +1
The woken application reissues the MQGET
- QMSTGET is now +102, QISTGET is now +1, and all applications are waiting in the adapter.

An application gets a message by message-id or correl-id

If the queue has not been indexed there is internal logic which searches along the queue for a message with matching message-id or correl-did. For example if there were 1000 messages on the queue, and the message was not found:

QMSTGET is now + 1, QISTMGET is now +1000.

An application gets a message by filter or message property

For example get the next message where the property color=”red”. This is like the previous case. The queue has to be searched looking for the specified property in the message header.

For example if there were 1000 messages on the queue, and the message was not found:

QMSTGET is now + 1, QISTMGET is now +1000.

Should you compare QMSTGET and QISTMGET?

If you gave me the two values, it would be very hard to draw any conclusions from it. Where it might be useful is comparing the difference over time. It delta or ratio changes, then it is likely that something has changed in your system, and could be a hint to go sniffing around.

Of course the delta or difference is likely to change with time of day, and day of week, so make sure you compare a similar time period.

Where’s my publish?

Like many things I do, it all started with an easy problem. I had an application which subscribed to a topic, it published on a topic string, then got the published message. Another application subscribed on the same topic string but did not get the message. I’ll leave clues for the experts to spot as I explain the progress I made.

The first complication was the subscribing and publishing application was in Python on z/OS (which runs in ASCII), and the other application was written in C using the default EBCDIC. I had to spend time working out how to convert from ASCII to EBCDIC. (When using CHARV you can specify a string and its code page and have MQ do it for you automatically – easy once you know which code page to use.) For other strings I had to convert manually using the A2E function from C run time.

There are some commands for displaying status of pub sub, it took a little while to understand them and give me the data I wanted.

For example

My application did a subscription with topic string “/currency/rate/EUR/GBP”.
The command gave

DIS TPSTATUS(‘/currency/rate/EUR/GBP’)
CSQM297I … CSQMDRTC NO TPSTATUS FOUND MATCHING REQUEST CRITERIA

Once I had opened the topic using the topic string, I got

CSQM201I … CSQMDRTC DIS TPSTATUS DETAILS
TPSTATUS(/currency/rate/EUR/GBP)
TYPE(TOPIC)
DEFPRESP(SYNC)
PUB(ENABLED)
SUB(ENABLED)
ADMIN()
RETAINED(NO)
PUBCOUNT(0)
SUBCOUNT(1)
PUBSCOPE(ALL)
SUBSCOPE(ALL)
…

I set up the subscription using Python

topic_string = ‘/currency/rate/EUR/GBP’
sub_desc = pymqi.SD() # create the basic subscription
sub_desc[‘Options’] = pymqi.CMQC.MQSO_CREATE + pymqi.CMQC.MQSO_RESUME +
pymqi.CMQC.MQSO_DURABLE + pymqi.CMQC.MQSO_MANAGED
sub_desc.set_vs(‘SubName’, “MYSUB” )
sub_desc.set_vs(‘ObjectString’, topic_string)

The code to get the subscribed message was

get_opts = pymqi.GMO(
MsgHandle=hMsg.msg_handle,
Options=pymqi.CMQC.MQGMO_NO_SYNCPOINT +
pymqi.CMQC.MQGMO_CONVERT +
pymqi.CMQC.MQGMO_PROPERTIES_IN_HANDLE +
pymqi.CMQC.MQGMO_FAIL_IF_QUIESCING +
pymqi.CMQC.MQGMO_WAIT)
get_opts[‘WaitInterval’] = 1000
data = sub.get(None, pymqi.md(), get_opts)
print(‘Received data: [%s]’ % data)

The code to publish to a topic was

msg = ‘1.3961’
topic = pymqi.Topic(qmgr, topic_string=topic_string)
topic.open(open_opts=pymqi.CMQC.MQOO_OUTPUT)
topic.close()

The Python program was subscribe, publish to topic, get the message.

When I ran the code, no messages were published. I tried changing the topic_string to ‘/currency/rate/EUR/USD’, that had no effect. Eventually I tracked down a code page problem in my code; I fixed that – but the program still did not publish a message.

The more knowledgable people reading this may have spotted one problem.

The first time the program ran, the subscription code created a SUB(MYSUB) with the given topic string (‘/currency/rate/EUR/USD’). When I changed the topic string to ‘/currency/rate/EUR/GBP’, and published a message, the subscription was using the original topic string with USD!, but publishing to GBP. Any changes to the SUBscription are ignored unless MQSO_ALTER is specified.

I deleted the SUB and reran my application. Displaying the subscription (MYSUB) gave

CSQM201I %CSQ9 CSQMDRTC DIS SUB DETAILS 934
SUB(MYSUB)
SUBID(C3E2D8D4C3E2D8F94040404040404040DAFEED99504CE540)
DURABLE(YES)
SUBTYPE(API)
TOPICSTR(/currency/rate/EUR/GBP)
SUBLEVEL(1)
…

I can display the topic string and see what is subscribed to it

dis tpstatus(‘/currency/rate/EUR/GBP’) type(sub)

This gave two subscriptions:

TPSTATUS(/currency/rate/EUR/GBP)
TYPE(SUB)
SUBID(C3E2D8D4C3E2D8F94040404040404040DAFE062AED26E2C0)
DURABLE(YES)
SUBTYPE(ADMIN)
SUBUSER(IBMUSER)
…
NUMMSGS(12)

and

TPSTATUS(/currency/rate/EUR/GBP)
TYPE(SUB)
SUBID(C3E2D8D4C3E2D8F94040404040404040DAFC73649B3C7200)
DURABLE(YES)
SUBTYPE(ADMIN)
SUBUSER(IBMUSER)
…
NUMMSGS(0)

So one subscription has seen 12 messages, the other subscription has seen 0 messages. This does not look like a wrong topic string, as they are resported as part of the display tpstatus.

I could not find a way of displaying all the information about a subscription in one command. I had to use DIS TPSTATUS.. TYPE(SUB), then use cut and paste to issue the DIS SUB SUBID(….). (It would be much easier for the poor end users if there was an ALL option to display all this data in one go.)

For example

SUB(COLIN)
SUBID(C3E2D8D4C3E2D8F94040404040404040DAFC73649B3C7200)
DURABLE(YES)
SUBTYPE(ADMIN)
DISTYPE(RESOLVED)
TOPICSTR(/currency/rate/EUR/GBP)
DEST(CP0000)
DESTQMGR()
DESTCORL(C3E2D8D4C3E2D8F94040404040404040DAFC73649B3C7200)
TOPICOBJ()
PUBACCT(00000000000000000000000000000000000000000000000000000000…)
USERDATA(CZZZ)
SUBUSER(IBMUSER)
SUBLEVEL(1)
…

So we can see from this subscription the topic string being subscribed on, and the queue name being used.

This subscription had no messages published to it; see the DISPLAY TPSTATUS TYPE(SUB) field NUMMSGS. Those of you with a PhD in PubSub may have spotted the problem; it is very well hidden. It is all to do with PubLevel and SubLevel. (The documentation is very confusing, it implies a subscription can have more than one sublevel).

I think of it as logic within publish which says for each subscription

If SubLevel <= PubLevel then publish the message
else skip the publish

The subscription from the python code had SubLevel = 0. (This was latent bug – it should have been set to 1!
The SubLevel from my DEFINE SUB command was the default 1.
The PubLevel from the Python code was 0 – this was the problem.

So the publish to my manual DEFINE SUB was skipped, and the publish to the Python code worked because PubLevel = 0 matched SubLevel = 0

The message is being published – but it is not still not there.

When I restarted my queue manager and ran the test, the Python application got no message found, which was a surprise to me. When I reran it, with debug code enabled – the get worked, and carried on working all day. Next day the same problem occurred. Very strange – is the debug code affecting the messages ?

I then remembered the default syncpoint behaviour (one of those face palm moments). On midrange the default is to put out out sync-point, so the messages are immediately available. On z/OS the default is to put within sync-point. The messages are only visible after a commit, or the implicit commit at MQDISC. On z/OS the messages were in syncpoint, and there was no commit. When I ran my program the second time, it got the message from the first run, and so on!

I put the commit in – and it all worked.

Check list of what to check

Check you are subscribing to the correct topic string.

Plan carefully how you define your topic(strings).

If you want to have an application define a subscription, consider some defensive programming.

MQSO_CREATE will create a subscription based on the specified data. If it already exists report an error.
MQSO_CREATE + MQSO_RESUME will create a subscription based on the specified data. If it already exists it will not report an error. A second usage will not change the subscription.
MQSO_CREATE + MQSO_ALTER will create a subscription based on the specified data. A second usage will update the subscription. This could be considered dangerous if you have multiple applications running concurrently changing the topic string or other parameters.
MQSO_RESUME does not create a subscription, not updates it. it uses the information in the subscription object.

It would be safer for an Administrator to define the MQSUB, and the applications to refer to it. Do not allow application users to be able to define a subscription. They should use the pre-defined MQSUB and add the topic string to give more granular data. For example I could use a null object and have a topic string of /TOP/SECRET/DATA/SPIESIN/ENGLAND. If you haven’t set up security properly then I could access the data.

Check the PubLevel and the SubLevel.

If you are not using this functionality set PubLevel to 9 and SubLevel to 1 ( the defaults).

You can DISPLAY SUB(….) SUBLEVEL to see the specified value.

The PubLevel is specified in the MQPMO.PubLevel. There is no display command for this.

Check the sync-point options.

You should always, always, always specify MQPMO_NO_SYNCPOINT, or MQPMO_SYNCPOINT and the commit. Do not let it default in case someone ports your code to or from z/OS. You can waste days hunting down this problem.