PK54117: BUFFERS FOR DD NAME IMSMON ( DC MONITOR DCMON ) ALLOCATED BELOW THE LINE IF IMSMON DD ALLOCATED BY JCL VS DFSMDA

APAR status

• Closed as program error.

Error description

• Customer IMS control region abended S878 immediately after
  DC Monitor started. Analysis of dump showed that the failing
  GETMAIN was by DF/SMS open processing for DD IMSMON, and
  was for BUFNO*BLKSIZE in below the line private. In this
  case this was over 500K and this much storage was not available
  below the line. IMS doesn't use these buffers and normally
  prevents their allocation, for OLDS and SLDS, by setting
  JFCBUFNO to zero before issueing OPEN TYPEJ. This was not
  done in case of DD name IMSMON.
  The problem only occurs when IMSMON DD statement is specified
  in control region JCL. If dynamic allocation via DFSMDA member
  is used, problem does not occur.
  

Local fix

• Don't allocate IMSMON DD in JCL, use dynamic allocation.
  

Problem summary

• ****************************************************************
  * USERS AFFECTED: All IMS V910 users specify DCB=BUFNO=X on    *
  *                 the IMSMON DD statement.                     *
  ****************************************************************
  * PROBLEM DESCRIPTION: IMS Monitor output dataset was          *
  *                      allocated with //IMSMON DD statement    *
  *                      and DCB=BUFNO=X. ABEND878 occurred      *
  *                      when module DFSFDLS0 opened this        *
  *                      dataset.                                *
  ****************************************************************
  * RECOMMENDATION: INSTALL CORRECTIVE SERVICE FOR APAR/PTF      *
  ****************************************************************
  When module DFSFDLS0 opens the MONITOR dataset, it uses a DCB
  with BUFNO=0 so that OPEN will not obtain buffers.  However,
  if DCB=BUFNO=X is specified on the //IMSMON DD statement,
  buffers are obtained below 16M line. These buffers are never
  used, as IMS has its own buffers for the MONITOR dataset.
  
  DFSFDLS0 issues OPEN with TYPE=J, the value of DBCBUFNO is
  replaced by JFCBUFNO.  This causes ABEND878 if there is not
  enough storage below 16M.
  
  Additional keywords:  ABENDS878, S878
  

Problem conclusion

• AIDS: RIDS/DBRC RIDS/CMD DBRC CMD
    GEN:
  
  *** END IMS KEYWORDS ***
  The following change has been made to resolve the problem:
  
  **************
  *  DFSFDLS0  *
  **************
  
  The JFCBUFNO field in the JFCB is cleared to zero prior opening
  the MONITOR dataset.
  

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:

  PK61110 UK34134

Modules/Macros

• DFSFDLS0
  

Fix information

• Fixed component name

  IMS V9

• Fixed component ID

  5655J3800

Applicable component levels

• R900 PSY UK34134

     UP08/03/08 P F803 Ž