MQ slow dequeuing rates on a XMITQ

Question

We have been facing an issue where message rate of a xmitq is very slow comparing with what should be a normal performance. We have many other Qmgrs with bigger MQ flows that don't have the same issue.

Our HUB qmgr connects to business line in the same company HUB qmgr, and even the destination queues on their side being empty the flow is really slow.

At OS and Network level they say nothing can be done. At MQ we have changed the Buffersizes so it matches the OS level and uses the system tcp windows.

Now at MQ level we have the channel SDR setup with BATCHSZ to 100, but seems the receiver is configured with 30. We noticed that because we see messages flow in batches fof 30 messages. Also not sure if that is related but we see the XMITQ havs always 30 uncommited messages.

Our questiong for advice.

Would increase the BATCHSZ parameter on SDR/RCVR help the perfomance? Is there any other parameter at MQ level that could help it?

 DIS CHS(NAME) ALL

AMQ8417: Display Channel Status details.
 CHANNEL(QMGRA.QMGRB.T7)           CHLTYPE(SDR)
 BATCHES(234)                            BATCHSZ(30)
 BUFSRCVD(235)                           BUFSSENT(6391)
 BYTSRCVD(6996)                          BYTSSENT(14396692)
 CHSTADA(2020-04-16)                     CHSTATI(14.38.17)
 COMPHDR(NONE,NONE)                      COMPMSG(NONE,NONE)
 COMPRATE(0,0)                           COMPTIME(0,0)
 CONNAME(159.50.69.38(48702))            CURLUWID(398F3E5EEA43381C)
 CURMSGS(30)                             CURRENT
 CURSEQNO(43488865)                      EXITTIME(0,0)
 HBINT(300)                              INDOUBT(YES)
 JOBNAME(000051FC00000001)               LOCLADDR(10.185.8.122(54908))
 LONGRTS(999999999)                      LSTLUWID(398F3E5EE943381C)
 LSTMSGDA(2020-04-16)                    LSTMSGTI(14.49.46)
 LSTSEQNO(43488835)                      MCASTAT(RUNNING)
 MONCHL(HIGH)                            MSGS(6386)
 NETTIME(2789746,3087573)                NPMSPEED(NORMAL)
 RQMNAME(QMGRB)                       SHORTRTS(10)
 SSLCERTI(*******************)
 SSLKEYDA( )                             SSLKEYTI( )
 SSLPEER(*******************)
 SSLRKEYS(0)                             STATUS(RUNNING)
 STOPREQ(NO)                             SUBSTATE(RECEIVE)
 XBATCHSZ(23,7)                          XMITQ(QMGRB.X7)
 XQTIME(215757414,214033427)             RVERSION(08000008)
 RPRODUCT(MQMM)

qm.ini:

Log:
 LogPrimaryFiles=10
 LogSecondaryFiles=10
 LogFilePages=16384
 LogType=LINEAR
 LogBufferPages=4096
 LogPath=/apps/wmq/QMGR/log/QMGR/
 LogWriteIntegrity=SingleWrite
Service:
 Name=AuthorizationService
 EntryPoints=13
TCP:
 SvrSndBuffSize=0
 SvrRcvBuffSize=0 
 ServiceComponent:
 Service=AuthorizationService
 Name=MQSeries.UNIX.auth.service
 Module=/opt/mqm75/lib64/amqzfu
 ComponentDataSize=0
Channels:
 MaxChannels=500

UPDATED: 15:41 GMT

Just to update the information, both sides are now with BATCHSZ 100 and seems slightly.

AMQ8417: Display Channel Status details.
 CHANNEL(QMGRA.QMGRB.T7)           CHLTYPE(SDR)
 BATCHES(403)                            BATCHSZ(100)
 BUFSRCVD(405)                           BUFSSENT(23525)
 BYTSRCVD(11756)                         BYTSSENT(53751066)
 CHSTADA(2020-04-17)                     CHSTATI(15.13.51)
 COMPHDR(NONE,NONE)                      COMPMSG(NONE,NONE)
 COMPRATE(0,0)                           COMPTIME(0,0)
 CONNAME(159.50.69.38(48702))            CURLUWID(6D66985E94343410)
 CURMSGS(0)                              CURRENT
 CURSEQNO(44115897)                      EXITTIME(0,0)
 HBINT(300)                              INDOUBT(NO)
 JOBNAME(0000172A00000001)               LOCLADDR(10.185.8.122(2223))
 LONGRTS(999999999)                      LSTLUWID(6D66985E93343410)
 LSTMSGDA(2020-04-17)                    LSTMSGTI(15.30.06)
 LSTSEQNO(44115897)                      MCASTAT(RUNNING)
 MONCHL(HIGH)                            MSGS(23505)
 NETTIME(101563,480206)                  NPMSPEED(NORMAL)
 RQMNAME(QMGRB)                       SHORTRTS(10)
 SSLCERTI(*************************************)
 SSLKEYDA( )                             SSLKEYTI( )
 SSLPEER(****************************)
 SSLRKEYS(0)                             STATUS(RUNNING)
 STOPREQ(NO)                             SUBSTATE(MQGET)
 XBATCHSZ(1,1)                           XMITQ(QMGRB.X7)
 XQTIME(191225,794134)                   RVERSION(08000008)
 RPRODUCT(MQMM)

AMQ8450: Display queue status details.
 QUEUE(QMGRB.X7)                      TYPE(QUEUE)
 CURDEPTH(0)                             IPPROCS(1)
 LGETDATE(2020-04-17)                    LGETTIME(15.30.06)
 LPUTDATE(2020-04-17)                    LPUTTIME(15.30.06)
 MEDIALOG(S2488154.LOG)                  MONQ(LOW)
 MSGAGE(0)                               OPPROCS(9)
 QTIME(794134, 191225)                   UNCOM(NO)

Answer 1

A couple of things..

• You have XBATCHSZ(1,1) so your recent batch size is 1 message per batch.
• Total messages 23505 batches 403, so an average of 58 messages per batch. If your recent batch size is 1, then you must have had some larger (100?) batch sizes
• XQTIME 191225 is number of microseconds messages were on the xmit queue before being sent. This is 0.1 second!
• Nettime 101563 microseconds. This is a long time ( 0.1 seconds) 10,000 would be a good value. Compare this with a "TCP PING"
• BUFSSENT 23525 is similar to number of messages - so message size is typically under 32K. Bytessent. messages gives 2286 so small messages.

Things to check

• The queue at the remote end. Has it filled up? This would cause the sender queue to get more messages
• The nettime seems very long. Compare this with TCP Ping. Nettime can include slow IO at the remote end - or a queue full at the remote end
• XQTIME is high. This could be caused by sending applications not committing, or slow disk IO

I wrote "Why is my xmit queue filling up" in this blog
*Search for the title

have a read.

Capture these metrics over a day and see if they are typical

regards

Colin Paice

Answer 2

I'll put a few observations in this answer, but based on any further feedback I may add more.

---

You are running a very old version of the software on the sender side, MQ 7.5 went out of support almost two years ago (April 30 2018). IBM for a cost will provide extended support for an additional three years, so maybe you fall in that group. The 7.5.0.2 maintenance release itself came out in July 11th 2013, so it is almost seven years old at this point. I would strongly suggest you move to a newer version.

Note that MQ v8.0 goes out of support April 30 2020, and IBM just announced a few days ago that MQ v9.0 goes out of support September 30 2021. When you do migrate you should go with either 9.1 which has no announced end of support (they give five years minimum so it could be 2023) or go with the next version of MQ that should be out some time this year.

---

You mention setting the following:

TCP:
 SvrSndBuffSize=0
 SvrRcvBuffSize=0 

The above setting apply to the SVRCONN end of a client connection. You can see this in the MQ v7.5 Knowledge Center page WebSphere MQ>Configuring>Changing configuration information>Changing queue manager configuration information>TCP, LU62, NETBIOS, and SPX:

SvrSndBuffSize=32768|number
The size in bytes of the TCP/IP send buffer used by the server end of a client-connection server-connection channel.

SvrRcvBuffSize=32768|number
The size in bytes of the TCP/IP receive buffer used by the server end of a client-connection server-connection channel.

At IBM MQ v7.5.0.2 APAR IV58073 introduced the concept of setting various buffer settings to a value to 0 which means that it will allow the operating system defaults to be used. Unfortunately like many things in the Knowledge Center it does not look like IBM documented this correctly for 7.5.

You can however review the IBM MQ v8.0 Knowledge Center to get the full picture regarding these settings at the page Configuring>Changing configuration information>Changing queue manager configuration information>TCP, LU62, and NETBIOS, specifically you would want to set these two settings to have any impact on your Sender Channel:

SndBuffSize=number| 0
The size in bytes of the TCP/IP send buffer used by the sending end of channels. This stanza value can be overridden by a stanza more specific to the channel type, for example RcvSndBuffSize. If the value is set as zero, the operating system defaults are used. If no value is set, then the IBM MQ default, 32768, is used.

RcvSndBuffSize=number| 0
The size in bytes of the TCP/IP send buffer used by the sender end of a receiver channel. If the value is set as zero, the operating system defaults are used. If no value is set, then the IBM MQ default, 32768, is used.

---

Starting at IBM MQ v8.0 any newly created queue manager will have all of the following in the qm.ini:

TCP:
   SndBuffSize=0
   RcvBuffSize=0
   RcvSndBuffSize=0
   RcvRcvBuffSize=0
   ClntSndBuffSize=0
   ClntRcvBuffSize=0
   SvrSndBuffSize=0
   SvrRcvBuffSize=0

However, any queue manager that is upgraded will not by default get those settings, meaning if those are not present they will not be added, if they are present they will remain the same. If the setting is not present then as it says above "the IBM MQ default, 32768, is used."

I had extensive discussions with IBM support on this topic and came to the conclusion that they did not see any reason to not set it to 0, they only saw benefit in doing so, but with an abundance of caution they do not change it to 0 for you.

I would recommend you add all of those to your qm.ini, but at minimum add the two I highlighted above.

These are good setting to implement but may not solve your problem if nothing changed recently on either end. If however something did change, for example a network difference, or MQ was upgraded to 8.0.0.8 on the remote side, then this setting just might solve your problem.

---

In the channel status output two values are interesting:

1. NETTIME(2789746,3087573)
2. XQTIME(215757414,214033427)

NETTIME means that based on recent activity it took 2.7 seconds to receive a response from the RCVR channel, over a longer period of time it took 3.1 seconds to receive a response from the RCVR channel. Can you compare this to a TCP ping from the sender channel server to the receive channel server, 2.7 seconds for a response over the network seems excessive. In the presentation Keeping MQ Channels Up and Running given at Capitalware's MQ Technical Conference v2.0.1.4, Paul Clarke who used to work for IBM states "NETTIME only measures network time, and does not include the MQCMIT for example".

XQTIME means that based on recent activity and over a longer period of time it took ~215 seconds for a message on the XMITQ to be picked up by the SDR channel to be sent.

See below for how IBM documents these:

NETTIME
Amount of time, displayed in microseconds, to send a request to the remote end of the channel and receive a response. This time only measures the network time for such an operation. Two values are displayed:

• A value based on recent activity over a short period.
• A value based on activity over a longer period.

XQTIME
The time, in microseconds, that messages remained on the transmission queue before being retrieved. The time is measured from when the message is put onto the transmission queue until it is retrieved to be sent on the channel and, therefore, includes any interval caused by a delay in the putting application.
Two values are displayed:

• A value based on recent activity over a short period.
• A value based on activity over a longer period.

---

Information on the BATCHSZ channel parameter can be found in the IBM MQ v8.0 Knowledge Center page Reference>Configuration reference>Channel attributes>Channel attributes in alphabetical order>Batch size (BATCHSZ). I have quoted it and highlighted a few areas in bold.

This attribute is the maximum number of messages to be sent before a sync point is taken.

The batch size does not affect the way the channel transfers messages; messages are always transferred individually, but are committed or backed out as a batch.

To improve performance, you can set a batch size to define the maximum number of messages to be transferred between two sync points. The batch size to be used is negotiated when a channel starts, and the lower of the two channel definitions is taken. On some implementations, the batch size is calculated from the lowest of the two channel definitions and the two queue manager MAXUMSGS values. The actual size of a batch can be less; for example, a batch completes when there are no messages left on the transmission queue or the batch interval expires.

A large value for the batch size increases throughput, but recovery times are increased because there are more messages to back out and send again. The default BATCHSZ is 50, and you are advised to try that value first. You might choose a lower value for BATCHSZ if your communications are unreliable, making the need to recover more likely.

This attribute is valid for channel types of:

• Sender
• Server
• Receiver
• Requester
• Cluster sender
• Cluster receiver

---

Follow up questions:

1. Are the messages that are PUT to this XMITQ persistent?
   Answer: Yes, in our PROD env all messages are pesistent.
2. Have you had a recent increase in volume going to this XMITQ?
   Answer: No, we use a monitoring tools, we extracted a report that show very similar message rate during the period. The same rate over the last 2 weeks.
3. Do the putting applications set MQPMO_SYNCPOINT and then commit after 1 or more messages are PUT to the queue?
   Answer: I will check with the application team.