A fix is available
APAR status
Closed as program error.
Error description
Outbound traffic backed up on port 12001 waiting on the UCB lock. The lock contention is causing DUCB expansion and suspended SRBs that quickly exhaust ECSA. The current design that requires serializing EE outbound requests on a given port is unable to sustain high volume traffic.
Local fix
Problem summary
**************************************************************** * USERS AFFECTED: All users of the IBM Communications Server * * for z/OS Version 1 Releases 12 and 13 SNA: * * Enterprise Extender * **************************************************************** * PROBLEM DESCRIPTION: Abend ABEND4C5 reason code 74FF2500 * * when contention exists on the UCB lock * * for Enterprise Extender port 12001 * * traffic. * **************************************************************** * RECOMMENDATION: * **************************************************************** The problem is summarized as follows: 1) EE configuration consisted of multiple local VIPAs active with connections to over 10,000 EE partners. 2) Remote EE partners were being rebooted in large numbers. The remote partners are end nodes (EN) which require CP-CP and DLUS support. 3) The large scale network activity generated 1000s of data packets for port 12001. 4) Each of these packets must pass through the TCP/IP FastUDP layer, which acquires the UCB lock exclusively to update route as well as policy information. 5) In this configuration, a spike in network activity resulted in UCB port 12001 lock contention which caused TCP/IP DUCBs to become suspended. This leads to a slowdown of outbound EE traffic and a growth in ECSA. In this case, ECSA growth expands until it is exhausted leading to the reported abends. Note: In the dump provided, there were over 9000 DUCBs suspended on the UCB lock. The PTF for TCPIP APAR PI06478 must be installed before or concurrently with the PTF for this APAR.
Problem conclusion
Enterprise Extender processing for outbound traffic has been optimized to better handle large amounts of outbound traffic. The basic design is for VTAM to pass a queueing structure, IUTIPNEE, along with IUTIL PLISTs to the TCP/IP stack when crossing the IUTSAMEH connection. These queueing structures, IUTIPNEEs, allow for concurrent processing while setting a maximum number of outbound threads of execution that can potentially suspend on a UCB lock This design allows for 16 queueing structures for each port priority, and 16 queueing structures to handle ANR routed HPR traffic, for a given local static EE VIPA. These queueing structures are assigned to each line during activation for the life of the line. These new structures allow a serialization point for outbound traffic. If FastUDP is busy processing a previous signal for EE, a new request will simply queue up on this structure and exit processing. This exit alleviates the need for the running DUCB as well as the SRB itself. When the previous process finishes up the current request, it will simply continue to process the remaining elements until all outbound work is complete.
Temporary fix
********* * HIPER * *********
Comments
APAR Information
APAR number
OA43910
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
2013-11-19
Closed date
2013-12-03
Last modified date
2014-03-03
APAR is sysrouted FROM one or more of the following:
APAR is sysrouted TO one or more of the following:
UA71699 UA71698 OA44090
Modules/Macros
ISTAUCAL ISTAUCDL ISTAUCFT ISTAUCLA ISTAUNCB ISTIPNCB ISTRAFME ISTRAFM1 ISTRLN ISTRPCDU ISTRPNCB ISTTSC89
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.
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Document Information
Modified date:
03 March 2014