|
Problem IC71080
|
Status: Closed |
HWM TOO LOW DUE TO TIMING WINDOW WHEN NEW SMP EXTENT ALLOCATED, CAN LEAD TO DATA CORRUPTION |
| product: |
DB2 FOR LUW / DB2FORLUW / 980 - DB2 |
| Problem description: |
There is a very small timing window where we cache the value of
the last initialized SMP extent.
We then use this value to calculate the high-water mark.
If a new SMP extent gets allocated within that timing window
then we'll set the high-water mark to a value that is too low.
Various operations will result in this subsequently getting set
correctly, but it is possible for a tablespace reduce to occur
and we can get rid of extents after the high-water mark...
extents that are in use by the tablespace.
This results in data corruption.
When this happens one of the symptoms is at database start up
time
the tablespace will be put to OFFLINE state and the following
error
will appear in the db2diag.log:
2010-07-09-04.39.06.621170+120 I420281399A2620 LEVEL: Severe
PID : 10563 TID : 27 PROC : db2sysc
0
INSTANCE: db2 NODE : 000 DB : SAMPLE
APPHDL : 0-973 APPID: *LOCAL.db2pc1.100709023906
AUTHID : DB2
EDUID : 27 EDUNAME: db2agent (SAMPLE) 0
FUNCTION: DB2 UDB, buffer pool services, sqlb_verify_page,
probe:3
MESSAGE : ZRC=0x86020001=-2046689279=SQLB_BADP "page is bad"
DIA8400C A bad page was encountered.
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
11776007
DATA #4 : Object descriptor, PD_TYPE_SQLB_OBJECT_DESC, 72 bytes
Obj: {pool:9;obj:65534;type:14} Parent={9;65534}
lifeLSN: 000000000000
tid: 0 0 0
extentAnchor: 0
initEmpPages: 0
poolPage0: 0
poolflags: 2122
objectState: 0
lastSMP: 0
pageSize: 4096
extentSize: 8
bufferPoolID: 1
partialHash: 4059955209
bufferPool: 0x7ffffff9b713bb40
DATA #5 : Bitmask, 4 bytes
0x00000002
DATA #6 : Page header, PD_TYPE_SQLB_PAGE_HEAD, 48 bytes
pageHead: {pool:0;obj:0;type:0} PPNum:0 OPNum:0
begoff: 0
datlen: 0
pagebinx: 0
revnum: 0
pagelsn: 000000000000 flag: 0
signature: 0
cbits1to31: 0
cbits32to63: 0
CALLSTCK:
[0] 0x7FFFFFFF7B017F30
__1cZsqlbLogReadAttemptFailure6FIpnQSQdDLB_OBJECT_DESC_IpnJSQdDL
B_PAGE_ibLIpcpnMSQdDLB_GLOBALS__v_
+ 0x150
[1] 0x7FFFFFFF7B01C8B8
__1cQsqlb_verify_page6FpnJSQdDLB_PAGE_pnQSQdDLB_OBJECT_DESC_IIpn
MSQdDLB_GLOBALS_pL_i_
+ 0x598
[2] 0x7FFFFFFF7B01965C sqlbReadPage + 0xE84
[3] 0x7FFFFFFF7AFF9334
__1cTsqlbGetPageFromDisk6FpnLSQdDLB_FIX_CB_i_i_ + 0x2EC
[4] 0x7FFFFFFF7AF42404 __1cHsqlbfix6FpnLSQdDLB_FIX_CB__i_ +
0xA1C
[5] 0x7FFFFFFF7B07AFA0
__1cYsqlbFindNewHighWaterMark6FHIpnJSQdDLP_LSN8_LpnMSQdDLB_GLOBA
LS__i_
+ 0xC38
[6] 0x7FFFFFFF7B06F4F8
__1cQsqlbDMSStartPool6FpnMSQdDLB_GLOBALS_pnMSQdDLB_POOL_CB__i_ +
0x7B8
Another possible symptom is some objects in the tablespace will
have data beyond the
high water mark, resulting in data corruption in the objects.
Though the problem may
remain undetected until the object is accessed, running db2dart
/TS on the tablespace
will catch this. |
| Problem Summary: |
****************************************************************
* USERS AFFECTED: *
* ALL *
****************************************************************
* PROBLEM DESCRIPTION: *
* HWM TOO LOW DUE TO TIMING WINDOW WHEN NEW SMP *
* EXTENTALLOCATED, CAN LEAD TO DATA CORRUPTIONThere is a very *
* small timing window where we cache the valueofthe last *
* initialized SMP extent.We then use this value to calculate *
* the high-water mark.If a new SMP extent gets allocated *
* within that timing windowthen we'll set the high-water mark *
* to a value that is toolow.Various operations will result in *
* this subsequently gettingsetcorrectly, but it is possible *
* for a tablespace reduce tooccurand we can get rid of extents *
* after the high-water mark...extents that are in use by the *
* tablespace.This results in data corruption.When this happens *
* one of the symptoms is at database startuptimethe tablespace *
* will be put to OFFLINE state and thefollowingerrorwill *
* appear in the db2diag.log:2010-07-09-04.39.06.621170+120 *
* I420281399A2620 LEVEL:SeverePID : 10563 *
* TID : 27 PROC :db2sysc0INSTANCE: db2 *
* NODE : 000 DB : SAMPLEAPPHDL : 0-973 *
* APPID:*LOCAL.db2pc1.100709023906AUTHID : DB2EDUID : 27 *
* EDUNAME: db2agent (SAMPLE) 0FUNCTION: DB2 UDB, *
* buffer pool services, sqlb_verify_page,probe:3MESSAGE : *
* ZRC=0x86020001=-2046689279=SQLB_BADP "page is bad"DIA8400C A *
* bad page was encountered.DATA #1 : String, 64 bytesError *
* encountered trying to read a page - informationfollows :DATA *
* #2 : String, 23 bytesPage verification errorDATA #3 : Page *
* ID, PD_TYPE_SQLB_PAGE_ID, 4 bytes11776007DATA #4 : Object *
* descriptor, PD_TYPE_SQLB_OBJECT_DESC, 72bytesObj: *
* {pool:9;obj:65534;type:14} Parent={9;65534}lifeLSN: *
* 000000000000tid: 0 0 0extentAnchor: *
* 0initEmpPages: 0poolPage0: *
* 0poolflags: 2122objectState: *
* 0lastSMP: 0pageSize: *
* 4096extentSize: *
* 8bufferPoolID: 1partialHash: *
* 4059955209bufferPool: 0x7ffffff9b713bb40DATA #5 : *
* Bitmask, 4 bytes0x00000002DATA #6 : Page header, *
* PD_TYPE_SQLB_PAGE_HEAD, 48 bytespageHead: *
* {pool:0;obj:0;type:0} PPNum:0 OPNum:0begoff: *
* 0datlen: 0pagebinx: *
* 0revnum: 0pagelsn: 000000000000 *
* flag: 0signature: *
* 0cbits1to31: 0cbits32to63: *
* 0CALLSTCK:[0] *
* 0x7FFFFFFF7B017F30__1cZsqlbLogReadAttemptFailure6FIpnQSQdDLB_O
* 0x150[1] *
* 0x7FFFFFFF7B01C8B8__1cQsqlb_verify_page6FpnJSQdDLB_PAGE_pnQSQd
* 0x598[2] 0x7FFFFFFF7B01965C sqlbReadPage + 0xE84[3] *
* 0x7FFFFFFF7AFF9334__1cTsqlbGetPageFromDisk6FpnLSQdDLB_FIX_CB_i
* + 0x2EC[4] 0x7FFFFFFF7AF42404 *
* __1cHsqlbfix6FpnLSQdDLB_FIX_CB__i_+0xA1C[5] *
* 0x7FFFFFFF7B07AFA0__1cYsqlbFindNewHighWaterMark6FHIpnJSQdDLP_L
* 0xC38[6] *
* 0x7FFFFFFF7B06F4F8__1cQsqlbDMSStartPool6FpnMSQdDLB_GLOBALS_pnM
* possible symptom is some objects in the tablespacewillhave *
* data beyond thehigh water mark, resulting in data corruption *
* in theobjects.Though the problem mayremain undetected until *
* the object is accessed, runningdb2dart/TS on the *
* tablespacewill catch this. *
****************************************************************
* RECOMMENDATION: *
* Upgrade to DB2 version 9.8 and Fix Pack 0 *
**************************************************************** |
| Local Fix: |
Contact service when the above occurs. |
| available fix packs: |
DB2 Version 9.8 Fix Pack 4 for AIX and Linux
DB2 Version 9.8 Fix Pack 5 for AIX and Linux
|
| Solution |
Problem was first fixed in DB2 version 9.8 and Fix Pack 0 |
| Workaround |
not known / see Local fix |
| Timestamps |
Date - problem reported :
Date - problem closed :
Date - last modified :
| 10.09.2010
04.08.2011
04.08.2011 |
| Problem solved at the following versions (IBM BugInfos) |
9.8.
|
| Problem solved according to the fixlist(s) of the following version(s) |
| 9.8.0.4
|
 |
