When undoing (rolling back) a "CREATE TABLE" log record
(UNDOCREATE_OBJECT_DP) for a table containing a LOB object (e.g.
during crash recovery, rollforward, or HADR Standby processing),
a stale value of the extent anchor for the table may be left in
memory. Simplified, an extent anchor is the pointer to the first
extent used by the table.
If this is followed by an operation that requires the extent
anchor, for example extent movement, and the database has not
been restarted prior to this, the stale value will cause DB2 to
access an incorrect page pointed to by the stale extent anchor.
This will result in errors such as SQLB_BADHDR or SQLB_READERR.
So far the problem has been seen during extent movement. The
typical call stack contains:
sqlbScanAllEMPsForObject
sqlbFindEMPMappingMovedExtent
sqlbMoveHighestExtent
sqlbLockAndMoveExtents
sqlbExtentMovementEntryPoint
db2diag.log example showing a request to read a page from
pool:4;obj:4100, whereas a page from tbspSeed:4;obj:279 was
retrieved:
2012-02-25-07.41.35.182980-300 I233648186E4455 LEVEL:
Severe
PID : 28199 TID : 140497825818368 PROC :
db2sysc
INSTANCE: db2inst1 NODE : 000 DB :
SAMPLE
APPHDL : 0-62840 APPID: *LOCAL.DB2.120225124901
AUTHID : DB2INST1 HOSTNAME: localhost
EDUID : 6474 EDUNAME: db2agent (SAMPLE)
FUNCTION: DB2 UDB, buffer pool services, sqlb_verify_page,
probe:14
MESSAGE : ZRC=0x87020036=-2029912010=SQLB_BADHDR "Bad Page
Header"
DIA8547C An error occurred in a database page header.
DATA #1 : String, 64 bytes
Error encountered trying to read a page - information follows :
DATA #2 : String, 23 bytes
Page verification error
DATA #3 : Page ID, PD_TYPE_SQLB_PAGE_ID, 4 bytes
9416
DATA #4 : Object descriptor, PD_TYPE_SQLB_OBJECT_DESC, 96 bytes
Obj: {pool:4;obj:4100;type:67} Parent={4;4100}
<...skipping...>
DATA #6 : Page header, PD_TYPE_SQLB_PAGE_HEAD, 48 bytes
pageHead: {tbspSeed:4;obj:279;type:0} PPNum:9416 OPNum:16
<...skipping...>
CALLSTCK: (Static functions may not be resolved correctly, as
they are resolved to the nearest symbol)
[0] 0x00007FC8E07FB33E pdLog + 0x38E
[1] 0x00007FC8E206E801 sqlbLogReadAttemptFailure + 0x1E1
[2] 0x00007FC8E38C1B53 sqlbReadPage + 0xE13
[3] 0x00007FC8E38B7716 sqlbGetPageFromDisk + 0x5C6
[4] 0x00007FC8E389AA3F sqlbfix + 0x112F
[5] 0x00007FC8E079E2D7 sqlbFixPage + 0x17
[6] 0x00007FC8E20429D0 /home/svtdbm12/sqllib/lib64/libdb2e.so.1
+ 0x27619D0
[7] 0x00007FC8E204428A sqlbScanAllEMPsForObject + 0x2AA
[8] 0x00007FC8E2045408 sqlbFindEMPMappingMovedExtent + 0xA28
[9] 0x00007FC8E204639C sqlbMoveHighestExtent + 0x9EC
[10] 0x00007FC8E2048C69 sqlbLockAndMoveExtents + 0xEB9
[11] 0x00007FC8E2049C6C sqlbExtentMovementEntryPoint + 0xAC
[12] 0x00007FC8E0AC31CA sqleIndCoordProcessRequest + 0x7FA
[13] 0x00007FC8E0AD4556 sqeAgent::RunEDU + 0x2B6
[14] 0x00007FC8E1AD4A83 sqzEDUObj::EDUDriver + 0xF3
[15] 0x00007FC8E1AD4989 sqlzRunEDUP + 0x9
[16] 0x00007FC8E1562FEF sqloEDUEntry + 0x29F
[17] 0x00007FC8E6D465F0 /lib64/libpthread.so.0 + 0x75F0
[18] 0x00007FC8DE7C884D clone + 0x6D |
****************************************************************
* USERS AFFECTED: *
* See APAR Description *
****************************************************************
* PROBLEM DESCRIPTION: *
* See Error Description *
****************************************************************
* RECOMMENDATION: *
* Upgrade to DB2 for Linux, UNIX, and Windows 9.7 Fix Pack 7. *
**************************************************************** |
