IBM Support recently released a Support Doc which posed the question:-
Question
Is there a way to delete a single message from an MQ queue (arbitrary position in the queue)?
The document described a couple of options. In this post we cover how to do this using MQGem tools as several of them offer this capability. Open up the twisty for each tool to read how to do this.
Using MO71
In MO71 you can browse a list of messages on a queue, then from that list, select an individual message (or multiple messages if you need to). Then press the Delete button, or select Delete from the right-mouse button context menu and the selected message(s) will be deleted.
MO71 uses the MQ facility, get by message token, so only the exact message(s) that you select from the list will be deleted. While the position of the message on the queue is shown, this is not used for deletion and neither is Message Id, since there is no guarantee that this will be unique either. Each message on a queue is guaranteed to have a unique Message Token.
Alternatively, you can double click on a message from the list, to view the whole message individually. Then from that display, having checked all the details, and made sure it is the message you want to delete, you can press the Delete button, or select Delete from the context menu.
Take care when deleting messages from a production queue manager. Consider that it might be safer to Move the message(s) to a separate holding queue, just in case the message proves to be important after all. MO71 makes it simple to Move messages too. Just fill in the holding queue name, and then press the Move, rather than Delete, button.
Using the Q program
To delete a single message from an MQ queue using the Q program, you should first discover the message ID of the message you wish to delete, to ensure you are addressing the correct message that you intend to delete. Do this by displaying the messages on the queue like this:-
q -m MQG1 -i Q1 -dd
This will browse (-i) the messages on the queue and display the MQMD after the MQGET (-dd) allowing you to see the Message ID of each message on the queue. You will see output like this for each message:-
==============================================================
----- MQMD after MQGET -----
[ 324 bytes] Message Descriptor (MQMD)
Report :00000000
Message Type :8 (Datagram)
Format :'MQSTR ' (String)
Priority :0 (Lowest)
Persistence :0 (Not Persistent)
Message Id :414D51204D514731202020202020202099FA4A6020B74B02
A M Q M Q G 1 . ú J ` · K .
ReplyToQ :' '
ReplyToQMgr :'MQG1 '
Now you can copy that message ID and use it on another invocation of the Q program to delete that specific message from the queue.
q -m MQG1 -IQ1 -gxm:414D51204D514731202020202020202099FA4A6020B74B02
Bear in mind that message IDs are likely to be unique, but this is not guaranteed. It would be safer to move the messages to a separate queue, before deletion. This is simple to achieve using a command like the following:
q -m MQG1 -IQ1 -o HOLDING.Q -gxm:414D51204D514731202020202020202099FA4A6020B74B02
Using QLOAD
If you have already browsed the queue contents and output them to a file, you can find the message Id of the specific message you are attempting to address by looking for the Message Descriptor attribute “MSI”. Here is a snippet from a QLOAD file to show an example.
A FMT MQSTR
A PRI 0
A PER 0
A MSI 414D51204D514731202020202020202099FA4A6020B74B02
A COI 000000000000000000000000000000000000000000000000
Now you can copy that message ID and use it on another invocation of the QLOAD program to delete that specific message from the queue. We would recommend using QLOAD to actually move that message to an output file, in case you change your mind about deleting it!
qload -m MQG1 -IQ1 -f c:\temp\deletedmsg.qld -gxm414D51204D514731202020202020202099FA4A6020B74B02
Alternatively, you can use the very flexible search and filtering capabilities of QLOAD to narrow down your search of messages on the queue until you find the one you wish to delete, and then offload it to a file, or delete it entirely.
For example, this invocation removes all messages on a queue that are older than one week, and moves them instead to the named file:-
qload -m MQG1 -I Q1 -T7:0:0 -f c:\temp\oldmsgs.qld
Another example, here we remove messages larger than 1MB from a queue:-
qload -m MQG1 -I Q1 -z 1M -f c:\temp\bigmsgs.qld
A third example, here we remove message containing the string “Acme Limited”:-
qload -m MQG1 -I Q1 -s "Acme Limited" -f c:\temp\acmemsgs.qld
Using MQEdit
In MQEdit you can browse a list of messages on a queue, then from that list, select an individual message (or multiple messages if you need to). Then press the Delete button, or select Delete from the right-mouse button context menu.
MQEdit uses the MQ facility, get by message token, so only the exact message that you select from the list will be deleted. While the position of the message on the queue is shown, this is not used for deletion and neither is Message Id, since there is no guarantee that this will be unique either. Each message on a queue is guaranteed to have a unique Message Token.
Alternatively, you can double click on a message from the list, to view the whole message individually in the pane below, and then from that pane, having checked all the details, and made sure it is the message you want to delete, you can select “Delete Message” from the context menu.
Particularly for production queue managers, we would always suggest that it is safer to move message(s) to a holding queue rather than deleting them immediately. In MQEdit it is very simple to move a message between queues, all you need do is drag and drop the required message(s) from one queue to another. You can even copy and move messages between queue managers this way.
If you don’t have any of these tools, but would like to try any or all of them out, please contact support@mqgem.com and a 1-month trial licence will be sent to you with no obligation to buy. You can download the tools from our website.
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