PI35724: UNEXPECTED OLDS WAS REUSED AFTER BSN WRAPPED AND /NRE WARM START 15/03/24 PTF PECHANGE

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• After BSN wrapped to zero and one OLDS contains only one block
  with BSN=0, OLDS reuse order after /NRE Warm start was wrong.
  < Scenario >
  1. Normal shutdown IMS when it is using OLP00.
  2. Update all type48 log records in OLP00 by adding X'FFFFFFE2'
     to force BSN wrap in next restart.
  3. Restart IMS with /NRE FMT RS command.  => OLP01 was opened.
  4. /SWI OLDS
      DFS3257I ONLINE LOG NOW SWITCHED - FROM DFSOLP01 TO DFSOLP02
  5. /SWI OLDS
      DFS3257I ONLINE LOG NOW SWITCHED - FROM DFSOLP02 TO DFSOLP03
       ==>  OLP02 contains only one block with BSN=00000000
  6. Several /CHE command
      DFS3257I ONLINE LOG NOW SWITCHED - FROM DFSOLP03 TO DFSOLP04
  7. /CHE FREEZE.
      DFS994I *CHKPT 15034/143448**FREEZE*
      DFS3257I ONLINE LOG CLOSED ON DFSOLP04
  ---------------------------------------------------------------
   DSET entries in the last type4301 log record in OLP04;
    F0F4C000 0000001E 0000001F 0000001E 0000003C 00C216B8 00C21710
    F0F3C000 0000001E 00000001 0000001E 0000001E 00000000 00000000
    F0F2C000 0000001E 00000000 00000000 00000000 00000000 00000000
    F0F1C000 0000001E FFFFFFF6 FFFFFFFF FFFFFFFF 00000000 00000000
    F0F0C000 0000001E FFFFFFE3 FFFFFFF5 FFFFFFF5 00000000 00000000
    F0F5C000 0000001E 00000000 00000000 00000000 00C21608 00C21660
  .
   OLP02 has only one block with BSN=00000000.
   OLP04 is the current used OLDS.
   OLP05 was pre-openen but was not used.
  ----------------------------------------------------------------
  8. /NRE (warm start)
      DFS680I USING CHKPT 15034/143448
      DFS3257I ONLINE LOG NOW OPENED ON DFSOLP02 <= Why not OLP05?
  9. /SWI OLDS
      DFS3257I ONLINE LOG NOW SWITCHED - FROM DFSOLP02 TO DFSOLP05
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: All IMS V13 users                            *
  ****************************************************************
  * PROBLEM DESCRIPTION: After applying PM96824, IMS restart can *
  *                      incorrectly decide which OLDS should be *
  *                      used if one of the OLDS previously used *
  *                      only contained one block of data.       *
  ****************************************************************
  * RECOMMENDATION: INSTALL CORRECTIVE SERVICE FOR APAR/PTF      *
  ****************************************************************
  To determine which OLDS should be used first for the life of an
  IMS, IMS restart looks at the block sequence numbers (BSNs) in
  the type4301 log records to find the OLDS that contains the
  oldest data. During this checking, IMS can also determine that
  an OLDS is empty. After applying APAR PM96824, if IMS restart
  saw that an OLDS had the same beginning and ending BSNs, then
  IMS restart took that to mean that the OLDS was empty.
  
  This APAR adds a flag (LDSWRITN) that is set after a buffer
  has been successfully written to the OLDS. Now, instead of
  comparing the beginning and ending BSNs for an OLDS, restart
  checks this flag to determine whether or not an OLDS had data
  written to it.
  

Problem conclusion

• GEN:
  POSTREQ PI43906
  KEYWORDS:
  
  *** END IMS KEYWORDS ***
  Modules and macros changed:
  
  ************
  * LCDSECT  *
  ************
  Add flag LDSWRITN to LDSFLAG2
  
  ************
  * DFSFDLB0 *
  ************
  Upon a successful write to the OLDS, turn on LDSWRITN in the
  DSET entry that corresponds to the current OLDS.
  
  ************
  * DFSFDLR0 *
  ************
  Change the checks comparing starting and ending BSNs to
  checking LDSWRITN
  
  Copy LDSWRITN value from the temporary DSET entry to the real
  DSET entry to be used later.
  
  Copy BSN values from real DSET to temporary DSET if the temporar
  DSET is initialized as represented by zeroes for LDSBLKNO and th
  LDSBSEQ* values.
  
  ************
  * DFSFDLS0 *
  ************
  Change the check comparing starting and ending BSNs to
  checking LDSWRITN
  
  When writing the type4301 record, copy the first 5 words of the
  active DSET entry (in LDSETA) into the entry in the type4301
  record that represents the current OLDS. This updates the
  LDSWRITN flag as well as the 3 BSN values.
  
  ************
  * DFSFDLY0 *
  ************
  Change the check comparing starting and ending BSNs to
  checking LDSWRITN
  

Temporary fix

Comments

• REPINNED RP15/06/30 (ATXT) TO ADD POSTREQ PI43906 INFO.
   **** PE15/06/30 PTF IN ERROR. SEE APAR PI43906 FOR DESCRIPTION
  ×**** PE15/06/30 FIX IN ERROR. SEE APAR PI43906  FOR DESCRIPTION
  

APAR Information

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

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

  UI28314

Modules/Macros

• DFSFDLB0 DFSFDLR0 DFSFDLS0 DFSFDLY0 DFSLOG43 LCDSECT
  

Fix information

• Fixed component name

  IMS V13

• Fixed component ID

  5635A0400

Applicable component levels

• R300 PSY UI28314

     UP15/06/13 P F506 {

Fix is available

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