DB2 FOR LUW / DB2FORLUW / B50 - DB2

An extent move log record (OBJ_MOVE_ANCHOR and OBJ_MOVE_EXT)
will be replayed if the page storing an extent's location is
older than the extent move log record i.e page LSN < log record
LSN.

There are two actions required for moving extents - move extent
on disk and update any cached page locations. This APAR
addresses a bug where extent movement log records are skipped
(i.e. extent not moved on disk), but cached page locations are
updated. This usually will not be a problem, except if the
recovery window is very long. A long recovery window opens the
chance of updating cached page locations of extents that should
not be moved, but also belong to a very old extent movement.
This can cause pages to be read from the wrong position in the
tablespace and can lead to read errors during recovery. One such
error can be found below:


2020-01-22-13.12.41.408368-300 I29438705E1403       LEVEL: Error
PID     : 162709               TID : 17690898919776 PROC :
db2sysc 8
APPHDL  : 0-33175              APPID: XXXX
EDUID   : 4084                 EDUNAME: db2redow (XXXX) 8
FUNCTION: DB2 UDB, buffer pool services, sqlbRedoUpdateEMP,
probe:814
MESSAGE : ZRC=0x8402008F=-2080243569=SQLB_READERR
          "Non-critical I/O or verification error encountered
during page read from disk."
DATA #1 : Object descriptor, PD_TYPE_SQLB_OBJECT_DESC, 104 bytes
    Obj: {pool:16;obj:292;type:71} Parent={16;292}
    lifeLSN:       00000000BA992AB2
    tid:           0 0  0
    extentAnchor:             5890216
    initEmpPages:                   0
    poolPage0:                      0
    poolflags:   0x              3122
    objectState: 0x             80027
    lastSMP:                        0
  pageSize:                   32768
  extentSize:                     4
  bufferPoolID:                   1
  partialHash:           1176764432
  objDescAttributes:                  0
  objDescEHLState: 0x0000100a801295df
  bufferPool:    0x00001000b1d746e0
  pdef:          0x0000100a72861b20
DATA #2 : Page ID, PD_TYPE_SQLB_PAGE_ID, 4 bytes
6990309
DATA #3 : Page ID, PD_TYPE_SQLB_PAGE_ID, 4 bytes
5

****************************************************************
* USERS AFFECTED:                                              *
* all                                                          *
****************************************************************
* PROBLEM DESCRIPTION:                                         *
* See Error Description                                        *
****************************************************************
* RECOMMENDATION:                                              *
* Upgrade to Db2 11.5m3fp0 or later                            *
****************************************************************

Avoid running extent movement (ALTER TABLESPACE ... REDUCE MAX
and ALTER TABLESPACE ... LOWER HIGH WATER MARK). If extent
movement is urgently required, ensure that the recovery window
is small before running extent movement. This can be checked by
running the following command and testing if the OLDEST_TX_LSN
is close to CURRENT_LSN and no indoubt transactions exist on the
database (db2 "select MEMBER, OLDEST_TX_LSN, CURRENT_LSN,
NUM_INDOUBT_TRANS from table (mon_get_transaction_log(-2)) as
t". This reduces that chances that an old extent movement log
record will be replayed incorrectly if recovery is required.

not known / see Local fix

forerunner  : 
follow-up : IT31893 

Date  - problem reported    :
Date  - problem closed      :
Date  - last modified       :

18.02.2020
24.04.2020
24.04.2020