PQ79621: Slow outbound data throughput when using few connections.

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• Performance for outbound data throughput can be slow when the
  number of connections using a blocking device are few (worst
  case 1 connection).
  
  
  Verification Steps:
  Gather a TCPIP Packet TRACE and look for up to 100ms delays
  between packets in streaming data and verify only a few
  connections are using the same device.
  

Local fix

• Overall throughput will increase if more connections send data
  over the same device.
  

Problem summary

• ****************************************************************
  * USERS AFFECTED: All users of the Communications Server for   *
  *                 z/OS Version 1 Release 5 IP                  *
  ****************************************************************
  * PROBLEM DESCRIPTION: Outbound throughput over a blocking     *
  *                      enabled device may be slow.             *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  The blocking algorithm used to optimize the outbound data path
  periodically performs an experimental increase in the blocking
  factor.  The algorithm incorrectly decrements the number of
  queued messages prior to determining if the new experimental
  factor is causing adverse delays.  When the number of queued
  messages is 1, the adjusted value becomes 0 and the blocking
  factor does not appear to be causing any delays in traffic.
  
  The increased blocking factor will cause a delay in the
  movement of data from the TCPIP stack to the network device.
  This delay may cause a measurable slowdown in throughput.
  
  The smaller the number of connections sending data over the
  device, the more likely this problem is to occur.
  +-------------------------------------------------------------+
  + 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

• The BKALGO1 blocking algorithm has been amended to account for
  a single queued message.
  
  * Cross Reference between External and Internal Names
  

Temporary fix

• *********
  * HIPER *
  *********
  

Comments

APAR Information

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

  PQ77674

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

  UQ81753

Modules/Macros

• BKALGO1  EZBIFOUT
  

Fix information

• Fixed component name

  TCP/IP V3 MVS

• Fixed component ID

  5655HAL00

Applicable component levels

• R150 PSY UQ81753

     UP03/11/21 P F311 Ž

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.