A fix is available
APAR status
Closed as program error.
Error description
Applications got an abend0C4 in DSNLXCMT +02f8 and DB2 crashed with abend04E RC00D94001 . Subsequent analysis showed a 1-bit overlay in a control block (QRDA) caused by a REORG utility with DISCARD option that had run to successful completion a few moments earlier. Additional investigation concluded the following scenarios are exposed to this: 1-REORG DISCARD is run and performs table space type conversion from single table linear or non-UTS segmented table space to PBG. 2- REORG DISCARD on non-partitioned tablespace (with or without pending alters or extended page conversion) and the ptf for apar PI85843 is applied on subsystem. This apar further exploited a base code bug that has been there since Db2 V10.
Local fix
Removing the PTF of PI85843 will highly diminish the chance for the problem to occur, but the error will completely disappear by avoiding DISCARD in REORG until a fix can be provided.
Problem summary
**************************************************************** * USERS AFFECTED: All Db2 11 for z/OS users of REORG * * TABLESPACE utility performing table space * * type conversion to PBG or running on non- * * partitioned table space with APAR PI85843 * * PTF UI56994 applied. * **************************************************************** * PROBLEM DESCRIPTION: With APAR PI85843 / PTF UI56994 applied * * or when performing table space type * * conversion to PBG, a REORG TABLESPACE * * DISCARD on a non-partitioned table * * space resulted in a one bit storage * * overlay in above the bar storage. * **************************************************************** * RECOMMENDATION: Apply corrective PTF when available * **************************************************************** User ran a REORG TABLESPACE DISCARD on a non-partitioned table space, which executed and completed successfully. Then a short while later, Db2 abnormally terminated with ABEND0C4 DSNLXCMT + x'02F8' and ABEND04E 00D94001 due to a 1-bit storage overlay on an internal control structure in above the bar storage. The reported problem is caused by REORG DISCARD execution which overlaid one bit of storage in above the bar address when data is being discarded. This can happen in one of two scenarios: (1) User is performing a table space type conversion from a non-partitioned table space to PBG via the REORG TABLESPACE SHRLEVEL REFERENCE or CHANGE utility running with the DISCARD option (2) After applying APAR PI85843 / PTF UI56994, REORG TABLESPACE DISCARD is run on a non-partitioned table space. Note that due to the random nature of the one-bit storage overlay, varying symptoms could have occurred as a result. Additional keywords: ABENDS0C4 OFFSET02F8 SMCOVERLAY
Problem conclusion
Code has been modified to prevent the aforementioned storage overlay during REORG DISCARD execution.
Temporary fix
********* * HIPER * *********
Comments
APAR Information
APAR number
PH04166
Reported component name
DB2 OS/390 & Z/
Reported component ID
5740XYR00
Reported release
B10
Status
CLOSED PER
PE
YesPE
HIPER
YesHIPER
Special Attention
NoSpecatt / Xsystem
Submitted date
2018-10-17
Closed date
2018-12-18
Last modified date
2019-02-02
APAR is sysrouted FROM one or more of the following:
APAR is sysrouted TO one or more of the following:
UI60339
Modules/Macros
DSNURFBR DSNURFIT DSNURSCN
Fix information
Fixed component name
DB2 OS/390 & Z/
Fixed component ID
5740XYR00
Applicable component levels
RB10 PSY UI60339
UP19/01/03 P F901 «
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.
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Document Information
Modified date:
02 February 2019