OA33358: SLOW ZIIP ASSISTED IQDIO TRANSFER SPEED BECAUSE SRB LOCK IS NOT RELEASED

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• ISTLLCHI does not release the SRB lock
  (DINCB_Wr_Qpoint_WorkQ_zIIP_SRB_Lock) that is later checked by
  IUTLLCIZ to handle zIIP assisted IQDIO multiwrite traffic.  As a
  result IUTLLCIZ does not schedule a SRB to write the data and it
  takes the TCPIP retransmit timer expiration to redrive the write
  processing.  This results in slow transmission speeds.
  

Local fix

• Disable ZIIP assisted IQDIO Multiwrite
  

Problem summary

• ****************************************************************
  * USERS AFFECTED: All running zIIP_assisted IQDIO Multiwrite   *
  *                 (SIGA-wm) traffic.                           *
  ****************************************************************
  * PROBLEM DESCRIPTION: Slow throughput for zIIP_assisted       *
  *                      IQDIO Multiwrite traffic.               *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  ISTLLCHI is invoked to process IQDIO Multiwrite (SIGA-wm)
  traffic.  The SRB lock (DINCB_Wr_Qpoint_WorkQ_zIIP_SRB_Lock) is
  held upon entry and RPH_SIGAwm_zIIP_assist is on, indicating
  that only Qpoint_Index 3 is to be processed.
  
  In segment DoIO, the limit for the number of SBALs permitted for
  a single SRB thread (64) is reached, so local flag NextQpoint is
  turned on to indicate this and cause mainline processing to
  schedule any remaining work on the queue.  Coincidentally, there
  is no additional data, so NextQpoint is reset and Qpoint_Index
  is set to 4 as way of forcing the SRB lock to be released by the
  "look-again" logic at the end of mainline.
  
  However, Qpoint_Index is subsequently incremented, thus causing
  the test that drives the "look-again" logic to fail.  The thread
  exits with the SRB lock unintentionally held.  As a result,
  subsequent zIIP assisted IQDIO Multiwrite work transmitted via
  IUTLLCIZ is queued but not scheduled.  It takes the TCPIP
  retransmit timer expiration to eventually redrive the write
  processing.
  

Problem conclusion

• In ISTLLCHI, the test to see if the SRB lock should be released
  has been changed.  As long as Qpoint_Index is greater than the
  Data_Queue_upper_bound_num, the "look-again" logic that releases
  the SRB lock will be executed.
  
  ISTLLCM8 has been included for maintenance purposes only.
  

Temporary fix

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

Comments

APAR Information

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

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

  UA55589 UA55588 UA55590

Modules/Macros

• ISTLLCHI ISTLLCM8
  

Fix information

• Fixed component name

  VTAM V4 MVS/ESA

• Fixed component ID

  569511701

Applicable component levels

• R1A0 PSY UA55588

     UP10/09/14 P F009 Ž

• R1B0 PSY UA55589

     UP10/09/14 P F009 Ž

• R1C0 PSY UA55590

     UP10/09/14 P F009 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.