PK11357: NO STATUSGC GCSTAT STATGC RECEIVED WHEN CROSSING A UOW BOUNDARY AFTER A PRIOR SYNCPOINT TAKEN BEFORE 'GC' AND GU TO REPOSITION

APAR status

• Closed as program error.

Error description

• Customer using a PROCOPT=H PCB issues issues a CHKPT call
  while positioned in the middle of a UOW (i.e. before receiving
  'GC' status). In this case syncpoint was issued due to 'FW'
  status code. A GHU call was then issued to reposition the HSSP
  PCB since position is lost unless the syncpoint was issued
  due to 'GC' status. The GHU positioned the PCB to the last
  root in the UOW. A GN call was then issued, and customer
  expected to receive status 'GC' since a UOW boundary was crossed
  but received instead a blank status code.
  The problem here is that ECPBFLGM,EPCBFLMS is within the
  EPCB position information cleared at syncpoint by DBFSHDQ0.
  The GHU call will not set it - it's normally set on a move
  forward - and hence the next GN call when it detects crossing
  of a UOW boundary and calls DBFPGAP0, still fails to return
  'GC' status. DBFPGAP0 finds the read-ahead UXRB unreferenced
  and EPCBFLMS not set, so skips the setting of the flags needed
  to return a GC status code.
  This apar will also add servicability traces when an HSSP
  PCB is repositioned backwards rather than to the next UOW,
  so that the reason (which may be valid) can be determined
  from the IMS log.
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: IMSFP R910 DEDB PROCOPT=H users.             *
  ****************************************************************
  * PROBLEM DESCRIPTION: NO STATUSGC GCSTAT STATGC RECEIVED      *
  *                      WHEN CROSSING A UOW BOUNDARY AFTER A    *
  *                      PRIOR SYNCPOINT TAKEN BEFORE 'GC'       *
  *                      AND GU TO REPOSITION.                   *
  ****************************************************************
  * RECOMMENDATION: INSTALL CORRECTIVE SERVICE FOR APAR/PTF      *
  ****************************************************************
  This service corrects a problem when customer using PROCOPT=H
  PCB issues a CHKPT call while positioned in the middle of a
  UOW. In this case syncpoint was issued due to 'FW' status code.
  A GHU call was then issued to reposition the HSSP PCB since
  position is lost unless the syncpoint was issued due to 'GC'
  status. The GHU positioned the PCB to the last root in the UOW.
  A GN call was then issued, and customer expected to receive
  status 'GC' since a UOW boundary was crossed but received
  instead a blank status code.
  The problem was due to flag EPCBFLMS in field ECPBFLGM being
  cleared at syncpoint by DBFSHDQ0.  The GHU call will not set
  it - it's normally set on a move forward - and hence the next
  GN call when it detects crossing of a UOW boundary and calls
  DBFPGAP0, still fails to return 'GC' status. DBFPGAP0 finds the
  read-ahead UXRB unreferenced and EPCBFLMS not set, so it skips
  the setting of the flags needed to return a GC status code.
  This service will also add serviceability traces in log record
  type6707 when an HSSP PCB is repositioned backwards rather than
  to the next UOW, so that the reason can be determined from the
  IMS log.
  

Problem conclusion

• AIDS: RIDS/FP RIDS/DEDB FP DEDB
    DEP: NONE
    GEN:
  
  *** END IMS KEYWORDS ***
  The following changes have been made:
  
  DBFSHDQ0:  Add code to not clear the current DB DL/I position
             EPCBBPOS for procopt H.  When a UOW position is
             being restored for a PROCOPT=H EPCB, the control
             blocks EPST, EPCB, and SPCB will be saved in
             type6707 log record for diagnostic purpose.
  
  ILOGREC:   Add log record type6707.
  
  DFSL6701:  Add subtype X'07' for log record type 67.
  
  ----------------------------------------------------------------
  DOCUMENTATION CHANGE FOR APAR PK11357
  LY37-3203-01: IMS VERSION 9 DIAGNOSIS GUIDE AND REFERENCE
  -
  THE FOLLOWING TEXT DESCRIBES THE DOC CHANGE:
  -
  
  TABLE 8. IMS LOG RECORDS USED TO ANALYZE IMS PROBLEMS
  +--------------------------------------------------------------+
  | Type  Mapping Macro   Dsect    Why Written (Issuing Module)  |
  +--------------------------------------------------------------+
  |x'67'  DFSL6701        CTREC    X'07' A HSSP PCB is reposition|
  |                                backward rather than to the   |
  |                                next UOW.  The control blocks |
  |                                EPST, EPCB, and SPCB will be  |
  |                                snapped in this log record for|
  |                                diagnostic purpose. (DBFSHDQ0)|
  +--------------------------------------------------------------+
  

Temporary fix

Comments

APAR Information

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

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

  UK18003

Modules/Macros

• DBFSHDQ0 DFSL6701 ILOGREC
  

Fix information

• Fixed component name

  IMS V9

• Fixed component ID

  5655J3800

Applicable component levels

• R900 PSY UK18003

     UP06/09/22 P F609