PI36847: A LONG RUNNING REMOTE OFFLOADED QUERY FROM CONGNOS APPLICATION ENVIRONMENT

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• A remote offloaded query to the accelerator from Congnos
  application. The query ran for hours.
  ***************************************************************
  Additional Symptoms and Keywords:
   IDAA IDAAV4R1/K
   Performance PERF WAIT DELAY ELAPSED TIME
   ABEND0C4 AB0C4 S00C4 0C4
    0C4-00000010 00000010 RC00000010
     DSNLCKDS DSNLCKDS+1848 1848 OFFSET1848
   IFCID180 QWHS0180 IFCID 180
  

Local fix

• Increase DRDA query block size to 256K.
  

Problem summary

• ****************************************************************
  * USERS AFFECTED: All DB2 users of the IBM Data Analytics      *
  *                 Accelerator (IDAA).                          *
  ****************************************************************
  * PROBLEM DESCRIPTION: This APAR addresses two unrelated       *
  *                      symptoms:                               *
  *                      1. A remote query that is offloaded to  *
  *                         an accelerator exhibits a greater    *
  *                         elapsed time compared to the same    *
  *                         query executed on DB2.               *
  *                      2. When IFCID 180 trace is enabled,     *
  *                         DB2 encounters ABEND0C4-00000010 at  *
  *                         LOC=DSNLILLM.DSNLCKDS+1848           *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  The following two unrelated conditions are reported:
  1. An application, using the IBM Data Server Driver, connects
     to a DB2 for z/OS server and issues a query which DB2
     offloads to an accelerator.  The number of rows returned
     from the query is limited by the IBM Data Server Driver
     ROWSET attribute.  However, DB2 returns the entire query
     result set instead of only the number of rows needed to
     satisfy the request.  The excess rows returned results in
     greater elapsed time compared to the same query executed
     on DB2.
  2. Abend ABEND0C4-00000010 at LOC=DSNLILLM.DSNLCKDS+1848 may
     occur while writing an IFCID 180 trace record.  This abend
     results from an internal logic error during processing of a
     partial DRDA DSS header.
     This abend is not limited to query offload processing, and
     can occur for any remote request whenever IFCID 180 tracing
     is enabled.
  

Problem conclusion

• DB2 has been changed as follows:
  1. Instead of returning the entire result set during a remote
     query offload, DB2 will now return only the rows needed to
     satisfy the request.
  2. DB2 will now correctly process partial DRDA DSS headers when
     writing an IFCID 180 trace record.
  

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:

  UI27247 UI27248

Modules/Macros

• DSNLCKDS DSNLZHC1
  

Fix information

• Fixed component name

  DB2 OS/390 & Z/

• Fixed component ID

  5740XYR00

Applicable component levels

• RA10 PSY UI27247

     UP15/05/15 P F505

• RB10 PSY UI27248

     UP15/05/15 P F505

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.