A fix is available
APAR status
Closed as program error.
Error description
Connections traversing hipersockets experience performance degradation, the results of which range from slow data tranfers to connection termination. The problem may not occur immediately after an IPL, but instead make take several days to surface. Some of the symptoms include: 1. Packet traces taken on both systems will show data leaving one system and never arriving on the other, or it will show the packets leaving one system but arriving at the other significantly later. 2. Large packets are sent, but do not arrive until a small packet traverses the same hipersocket (the small packet may trigger the actual transmission of the other data across the hipersocket). This only affects connections which use zIIP assisted IQDIOMULTIWRITE, configured on the GLOBALCONFIG statement of the TCPIP profile.
Local fix
Disable the zIIP assisted IQDIOMULTIWRITE function by setting the GLOBALCONFIG ZIIP subparamater to NOIQDIOMULTIWRITE, either explicitly or by default (by simply removing the the subparamater value of IQDIOMULTIWRITE).
Problem summary
**************************************************************** * USERS AFFECTED: All using Hipersockets IQDMULTIWRITE with * * zIIP Assist. * **************************************************************** * PROBLEM DESCRIPTION: Various symptoms (e.g., slow data * * tranfer, connection termination) on * * hipersockets devices running * * IQDMULTIWRITE with zIIP Assist. * **************************************************************** * RECOMMENDATION: * **************************************************************** The problem may be summarized as follows: 1. Packets are sent from the TCP/IP IF layer to VTAM (IUTLLCIZ). They are destined to be written to a hipersockets device utilizing the IQDIOMULTIWRITE with zIIP assist functionality. An enclave SRB is scheduled in this case. 2. This gives control to the exit routine IUTLLCZ1, which sets up an RPH and passes the data to ISTLLCHI via escape. 3. However, niether RPH_Pass_Thread nor RPH_Passed_Work are explicitly set, so their values are residual based on previous uses of that particular DWA workarea. The fatal residual combination of RPH_Pass_Thread=ON and RPH_Passed_Work=0 causes ISTLLCHI to exit without resetting the synch byte (DINCB_Wr_Qpoint_WorkQ_zIIP_SRB_Lock) for the queue DINCB_Wr_Qpoint_WorkQ(3), thus leaving that SRB_Lock held erroneously. 4. Any subsequent packets sent over this hipersockets device get queued to the DINCB work queue, but do not get processed because the synch byte is on. 5. The data is left stranded on the queue until another packet (not using IQDIOMULTIWRITE with zIIP assist) is sent to the same destination. That then causes all elements on the queue to be processed.
Problem conclusion
IUTLLCZ1 has been changed to explicitly set RPH_Pass_Thread=OFF and RPH_Passed_Work=0 during RPH setup. This will ensure DINCB_Wr_Qpoint_WorkQ_zIIP_SRB_Lock is maintained properly by ISTLLCHI. ISTLLCM8 has been included for maintenance purposes.
Temporary fix
********* * HIPER * *********
Comments
APAR Information
APAR number
OA40894
Reported component name
VTAM V4 MVS/ESA
Reported component ID
569511701
Reported release
1D0
Status
CLOSED PER
PE
NoPE
HIPER
YesHIPER
Special Attention
NoSpecatt / Xsystem
Submitted date
2012-11-28
Closed date
2012-12-05
Last modified date
2013-02-04
APAR is sysrouted FROM one or more of the following:
APAR is sysrouted TO one or more of the following:
UA67411 UA67412
Modules/Macros
ISTLLCM8 IUTLLCIZ
Fix information
Fixed component name
VTAM V4 MVS/ESA
Fixed component ID
569511701
Applicable component levels
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.
[{"Business Unit":{"code":"BU054","label":"Systems w\/TPS"},"Product":{"code":"SG19M","label":"APARs - z\/OS environment"},"Component":"","ARM Category":[],"Platform":[{"code":"PF025","label":"Platform Independent"}],"Version":"1D0","Edition":"","Line of Business":{"code":"","label":""}},{"Business Unit":{"code":"BU054","label":"Systems w\/TPS"},"Product":{"code":"SSCY4DZ","label":"DO NOT USE"},"Component":"","ARM Category":[],"Platform":[{"code":"PF025","label":"Platform Independent"}],"Version":"1D0","Edition":"","Line of Business":{"code":"","label":""}}]
Document Information
Modified date:
04 February 2013