OA47064: AFTER INSTALLATION OF UA75442/UA75443 FOR OA46028, ABEND0C4 ERRORS OCCUR IN VSM MODULES DURING IMS MPP REGION TERMINATION.

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• After applying z/OS R13 RTM PTF UA75442, customers experience
  ABEND0C4 errors in VSM modules due to an overlay to field TCBMSS
  which is used as a queue anchor by the z/OS VSM component.  It
  has been determined that the recompile of RTM module IEAVTSKT
  (which drives resource managers) caused internal register usage
  to change, exposing a latent error in MQ resource manager module
  CSQQSSON when it was called by RTM.  CSQQSSON was using register
  11 without it ever having been initialized.  After the recompile
  of IEAVTSKT for APAR OA46028, register 11 residually pointed to
  a TCB when CSQQSSON was driven.  CSQQSSON used this register and
  ended up overlaying the TCBMSS field at TCB+X'18'.  This field
  is used by VSM as a control block anchor, so the overlay led to
  program checks in various VSM modules including but not limited
  to IGVFSDQE, IGVGPVT, IGVRSRTN, IGVFPVT, IGVQSPET, and IGVGCAS.
  Symptoms of ABENDB78 RC04 in IGVSTSKT and IGVQSPET have also
  been observed.  These abends occur during shutdown of IMS MPP
  regions and cause significant impact with multiple abends and
  a possible hang.
  
  Note that the VSM control block corruption that results in
  ABEND0C4 errors in VSM code has also been seen to result in
  bad storage addresses being handed out on GETMAIN and STORAGE
  OBTAIN requests made under the TCB with the damaged TCBMSS
  field.  This can lead to many other unpredictable symptoms
  including storage overlays in any area of STORAGE.  In one
  instance an SDWA was seen overlaying a VTAM MPST control
  block, but this is just an example and many other variations
  are possible.
  
  This problem is seen with these symptoms when z/OS is at release
  HBB7780 ( R13 ) and MQ is at WebSphere MQ 7.1.0.  The CSQQSSON
  defect was introduced via PTF UI11931 (HMS7100), which has now
  been PE'd by MQ APAR PI34742.  Note that this MQ PTF can also
  run on z/OS R2.1, but due to different compiler register usage
  in the RTM R2.1 PTF UA75443, very different (and potentially
  undetected) symptoms could result.
  
  PE INFORMATION:
  
  USERS AFFECTED: Users with either z/OS R13 (HBB7780) PTF UA75442
  or z/OS R2.1 (HBB7790) PTF UA75443, along with WebSphere MQ
  7.1.0 PTF UI11931.  Note that this problem is likely to be seen
  after recent installation of the z/OS PTF, which exposes a
  latent issue in the WMQ PTF UI11931.
  
  USER IMPACT: APAR OA46028 fixed the problem it reported but
  introduced a new problem.  The fix for OA46028 was correct, but
  due to a change in compiler register usage, the new RTM code
  exposed a latent defect in register usage by a routine that it
  interfaced with, CSQQSSON.  Module CSQQSSON overlaid a TCB at
  +X'18', the TCBMSS field.  This causes many abends in VSM. This
  problem occurs during IMS MPP region termination and cause
  significant impact to IMS.  The problem for which OA46028 was
  opened is of significantly less impact than this problem that is
  exposed through application of the RTM PTFs.  Users are advised
  to remove the RTM PTF until relief for the MQ issue described by
  WMQ APAR PI34742 is available and installed on their system.
  Note that due to different compiler register usage in the z/OS
  R13 RTM PTF versus the z/OS R2.1 RTM PTF, z/OS R13 customers are
  more likely to see significant impact.  However, exposure exists
  at both releases, so regardless of whether the user is at z/OS
  R13 or z/OS R2.1, the recommendation is to remove the RTM PTF.
  
  VERIFICATION STEPS
  1) Various VSM abends during IMS MPP region shutdown with WMQ R7
     PTF UI11931 and z/OS R13 RTM PTF UA75442 both applied.
  
  OR
  
  2) Unpredictable symptoms during IMS MPP region termination with
     WMQ R7 PTF UI11931 and z/OS RTM PTF UA75443 both applied.
  

Local fix

• Remove z/OS RTM PTF UA75442/UA75443 or apply APARFIX for
  WMQ APAR PI34742 which PE's MQ PTF UI11931.
  

Problem summary

• ****************************************************************
  * USERS AFFECTED: Users with either z/OS R13 (HBB7780) PTF     *
  *                 UA75442 or z/OS R2.1 (HBB7790) PTF UA75443,  *
  *                 along with WebSphere MQ 7.1.0 PTF UI11931.   *
  ****************************************************************
  * PROBLEM DESCRIPTION: ABEND0C4 during IMS MPP termination     *
  *                      due to overlay of TCBMSS by module      *
  *                      CSQQSSON.                               *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  The PTFs for RTM APAR OA46028 were PE'd to protect customers
  from the overlay reported by MQ APAR PI34742.  There was no
  actual problem with the RTM fix, but it changed the nature
  of the MQ overlay from harmless to harmful.  This APAR
  addresses the RTM PE by shipping a harmless macro change to
  IHASDWA with a prereq of the PTFs for OA46028 and a req of
  the fixing PTF for PI34742.
  

Problem conclusion

• See the Problem Summary
  

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:

  UA76973 UA76974

Modules/Macros

• IHASDWA
  

Fix information

• Fixed component name

  RTM

• Fixed component ID

  5752SCRTM

Applicable component levels

• R780 PSY UA76973

     UP15/04/29 P F504 «

• R790 PSY UA76974

     UP15/04/29 P F504 «

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.