PM73355: SLOW NETWORK TRANSFER RATES FOR MQSERIES CONNECTIONS

A fix is available

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You can track all active APARs for this component.

APAR status

  • Closed as program error.

Error description

  • MQSeries connections (or any application that tends to send
    data in large bursts) have the potential to experience low
    throughput rates to partner systems.
    
    Symptoms include:
    
    1. High number of messages per second that hit XMITQ to result
       in the latency spikes.
    
    2. SMF data (types 115 and  116 for queue managers) shows long
       PUTs, buffer pool getting full, above-normal number of pages
       per I/O.
    
    3. RMF III report shows high CPU usage in CHINIT address space
       (e.g. 60-70%) in 10-second intervals for spikes in messages
       and latency.
    
    4. RMF III report shows significant CPU delays (> 10%) for
       CHINIT.
    
    This problem can also impact bulk transfer protocols (such as
    FTP or Connect:Direct) when the network has a high rate of
    packet loss or the sending application is not getting CPU or I/O
    resources when needed.
    
    
    
    Verification steps include:
    
    1. NETSTAT ALL on the individual connections and note the
       congestion window size as well as the calculated round-trip
       time.
    
       Only the outbound connection would be affected.  If the
       remote system's IP address is y.y.y.y and the MQ listener is
       is on port nnnn, the command would be:
    
         TSO:       NETSTAT ALL (IPPORT y.y.y.y+nnnn
         OpConsole: D TCPIP,,NETSTAT,ALL,IPPORT=y.y.y.y+nnnn
    
    2. Review the smoothed round trip time (is it more than a few
       ms)?
    
    3. Are there any retransmissions on the connection? If there are
       retransmissions, it is an indication of problems outside of
       z/OS and is an issue that would need to be corrected before
       analysis can be done for whether or not the APAR applies.
       If the problem appears to be outside of z/OS, then collect a
       network sniffer trace on a shadowed switch port.
    
    4. If the NETSTAT ALL report shows congestion window size
       increases with no decreases for a MQseries connection,
       then the APAR would apply.
    

Local fix

  • (None)
    
    KEYWORDS:
    MQ MQSERIES WINDOWSIZE CONGESTION WINDOW PERF PERFORMANCE
    LATENCY ROUNDTRIP RTT CHINIT XMITQ CPU DELAY TCP
    

Problem summary

  • ****************************************************************
    * USERS AFFECTED: All users of the IBM Communications Server   *
    *                 for z/OS Version 1 Release 13 IP             *
    ****************************************************************
    * PROBLEM DESCRIPTION: Slow network transfer rates for         *
    *                      TCPIP connections.                      *
    ****************************************************************
    * RECOMMENDATION:                                              *
    ****************************************************************
    TCPIP connections that send data in bursts cause the senders
    congestion window to be incorrectly reduced. The reduced
    congestion window causes poor connection performance.
    In some scenarios the performance may decrease enough to
    trigger a timeout failure at an application level.
    +-------------------------------------------------------------+
    + Please check our Communications Server for OS/390 homepages +
    + for common networking tips and fixes.  The URL for these    +
    + homepages can be found in Informational APAR II11334.       +
    +-------------------------------------------------------------+
    

Problem conclusion

  • TCPIP has been modified to limit congestion window reduction.
    
    * Cross Reference between External and Internal Names
    

Temporary fix

Comments

APAR Information

  • APAR number

    PM73355

  • Reported component name

    TCP/IP V3 MVS

  • Reported component ID

    5655HAL00

  • Reported release

    1D0

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    YesHIPER

  • Special Attention

    NoSpecatt

  • Submitted date

    2012-09-20

  • Closed date

    2012-10-09

  • Last modified date

    2013-02-12

  • APAR is sysrouted FROM one or more of the following:

  • APAR is sysrouted TO one or more of the following:

    UK82536

Modules/Macros

  • EZBTCFWR EZBTCSND EZBTLFWR EZBT6FWR EZBT6LWR
    EZBT6SND TCSNDINT T6SNDINT
    

Fix information

  • Fixed component name

    TCP/IP V3 MVS

  • Fixed component ID

    5655HAL00

Applicable component levels

  • R1D0 PSY UK82536

       UP12/11/15 P F211

Fix is available

  • Select the PTF appropriate for your component level. You will be required to sign in. Distribution on physical media is not available in all countries.



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Document information


More support for:

z/OS family

Software version:

1D0

Operating system(s):

z/OS

Reference #:

PM73355

Modified date:

2013-02-12

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