OA48273: ABEND0C4 PIC3B REGISTER 15 R15 DIRTY HIGH HALF AMODE64 after STORAGE OBTAIN - unpredictable results 15/07/14 PTF PECHANGE

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• With the apply of apar OA46291 (ptf UA90976),
  IAXVP was compiled with a different option.  This option
  resulted in an instruction that leaves register 15 content of
  00000010_yyyyyyyy, where previously it resulted in the high half
  of the register being cleared.  The x'10' in the high half is
  then used by the caller, unexpectedly and an Abend0C4-3B PIC3B
  results when in AMODE(64).
  
  This happened across a Storage Obtain/getmain call and the
  service documents that bits 0-31 of register 15 are
  unpredictable.  It is good programming practice to make sure
  your register is cleared before you use it.
  
  Depending upon the reaction of the code/subsystem/exit that
  encounters the dirty Reg15, unpredictable results may occur.
  While an ABEND0C4 Pic3B is the more common result, other
  situations may occur.  For example, IRLM, which received
  the dirty Reg15 checked it for the Return code.  It was doing a
  Conditional Getmain and thought that the Getmain was
  unsuccessful (when in reality it actually was successful), so it
  proceeded to reattempt the Getmain only to get the same results.
  Without limits in place, this Getmain was issued
  repeatedly until storage in the address space is exhausted with
  an ABEND878-10, causing the job or address space to crash.
  
  If any code expects zeroes in the high half of a register, the
  results of what may happen when the high half is not zeroes then
  becomes unpredictable, based on how the application/job behaves.
  
  Additional keywords: R2964/K   D/T2964
  
  00000010
  ERBMFCLS
  BPXLKLCP
  OEM software
  AMODE64
  
  Verification Steps:
  1. APAR OA46291 is applied (ptf UA90976 )
     In a dump:
     ip verbx nucmap
     f IAXVP       (you can search for any module that the ptfs
                    changed)
     ip list yyyyyyyy len(x'40')
       *NOTE* replace yyyyyyyy withe the address under location
              column from verbx nucmap
     If one of the mentioned PTFs applied proceed to step 2.
     If it is not applied, this  does not describe why your
     register may be dirty.
  
  2. check the value of register 15 in abend registers
     (Abend0C4-3B)
     In the cases where this was observed, R15 content that is
     dirty is x'10',
     example
     00000010_yyyyyyyy
     *NOTE* yyyyyyyy is irrelevent what content it is.
  
  3. If an Abend0C4-3B was observed, you may see close to the
     abend or directly before it in the system trace that a
     storage obtain or getmain occurred from the program that took
     the Abend0C4
  

Local fix

• By turning on the RSM Component Trace (CTRACE) the high order
  bits will be cleared during Ctrace processing in the module that
  experienced the issue.   The ctrace options selected below
  (HSPSCROL & ALLOC2G) were chosen since they would be less likely
  than other RSM options to be encountered on most customer
  systems.  However, if you either suspect that  both would
  be likely to be encountered frequently, or experience any
  issues when turning on Ctrace, please contact Level2 for further
  recommendations on other Ctrace options that can be chosen.
  
  ---------- Turn on RSM Ctrace ----------------------------
  
  There are two ways to turn the CTRACE on
  
  1. From the console
  
  TRACE CT,100M,COMP=SYSRSM
   R xx,OPTIONS=(BUFF=(7,60),HSPCACHE),END
  
  We do not anticipate there will be any impact from this option,
  as it is a fairly uncommon function.  If it happens that a
  customer does complain about a  performance from the above
  ctrace then you may use a different CTRACE option.  In that
  case, replace HSPCACHE with ALLOC2G.  So the reply would look
  like
  
   R xx,OPTIONS=(BUFF=(7,60),ALLOC2G),END
  
  
  or
  
  2. Through a PARMLIB member, so it is enabled at IPL
     automatically
  
     Create a CTIRSMxx member in PARMLIB with the following
     content:
  
     TRACEOPTS ON OPTIONS('BUFF=(7,60)','HSPCACHE')
  
     Add the following command to your COMMNDxx member in PARMLIB:
  
     TRACE CT,100M,COMP=SYSRSM,PARM=CTIRSMxx
  
     This will enable RSM trace at IPL time.
  
  As with option #1, if there is a performance impact from the
  HSPCACHE  option, ALLOC2G or HSPSCROL can be chosen.
  
  
  -------------------------------------------------------------
  
  You can Display the results of turning on/off the Ctrace with
  
  D TRACE,COMP=SYSRSM
  
  -------------------------------------------------------------
  
  To turn OFF the RSM Ctrace, in case any problems arise,  use
  
  TRACE CT,OFF,COMP=SYSRSM
  

Problem summary

• ****************************************************************
  * USERS AFFECTED: Users of HBB7790 who                         *
  *                 apply apar OA46291 (PTF UA90976).            *
  ****************************************************************
  * PROBLEM DESCRIPTION: ABEND0C4 PIC3B register 15 R15 dirty    *
  *                      high half AMODE64 after storage         *
  *                      obtain - unpredictable results          *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  With the apply of apar OA46291 (PTF UA90976),
  IAXVP was compiled with a different option.  This option
  resulted in an instruction that could corrupt the content
  of the high half of R15, where previously it resulted in
  the high half of R15 being cleared.
  This can lead to Abend0C4-3B PIC3B or unexpected results
  by the caller in AMODE(64).
  This happened across a Storage Obtain/getmain call and the
  service documents that bits 0-31 of register 15 are
  unpredictable.  It is good programming practice to make sure
  your register is cleared before you use it.
  

Problem conclusion

• The code in IAXVP is changed to clear the high half
  of the return code (R15).
  Additional keywords: R2964/K   D/T2964
  

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:

  UA78633

Modules/Macros

• IAXVP
  

Fix information

• Fixed component name

  RSM - REAL STOR

• Fixed component ID

  5752SC1CR

Applicable component levels

• R790 PSY UA78633

     UP15/08/26 P F508 ®

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.