APAR status
Closed as program error.
Error description
users could get down level page for lob objects defined with GBPCACHE SYSTEM. It caused storage overlay. SMCOVERLAY DB2OVRLAY/K sequence of events. -- 1. member A updates a lob data page and writes it out to dasd. 2. LOB becomes non-GBP-dependent. 3. LOB becomes GBP-dependent again. 4. Member A reformats(no-read GetPage) the page in it's local buffer pool and doesn't register the page to GBP 5. Member A writes reformated page out to DASD. 6. Meber B gets page from DASD, updates it and writes it to DASD. 7. Member A tests the page in it's local buffer pool and thinks it's valid, so it go ahead reads the page from it's local buffer pool. -- Since member A doesn't register the page at step 4, it doesn't receive cross invalidat at step 6. at step 7, it reads page from it's local buffer pool and skip updates made by member B at step Other possible symptoms: ABENDS0C4 0C4 00000010 RC10 PIC10 DSNB5PCO M=DSNTFRCV LOC DSNVSRX DSNVSRRX OFFSET03BE where the thread is the 010.PCOPCO01 thread ABEND0C4 00000038 RC38 PIC38 DSNTFRCV LOC=DSNIDM DSNB1REL OFFSET011C ABND 04E 00C90101 M=N C=101 RDS -SQL DSNTFRCV LOC=DSNIDM DSNOTCSO 5063 ERQUAL5063 ABENDS0C6 ABEND0C6 0C6 00000006 RC06 DSNB5PCO M=DSNTFRCV PSW=470C200189094203 A=00D7
Local fix
ALTER lob objects from GBPCACHE SYSTEM to GBPCACHE CHANGE.
Problem summary
**************************************************************** * USERS AFFECTED: DB2 data sharing users, with table spaces or * * indexes defined as GBPCACHE NONE, or LOB * * spaces defined as GBPCACHE SYSTEM, and with * * PM67544 (UK82633) and OA38419 (UA66420, * * UA66421) applied, and with coupling * * facilities at CFLEVEL 17 or higher. * **************************************************************** * PROBLEM DESCRIPTION: Lost updates in data sharing. * * * * Corrupted data can result in any of * * the following symptoms: * * - Incorrect output, INCORROUT. * * - ABEND04E RC00C90101, RC00C90102, * * RC00C90105, or RC00C902xx in * * various CSECTs. * * - Data/index inconsistencies reported * * by the CHECK INDEX utility. * * - Page regression reported by the * * DSN1LOGP utility. * * * * If the object of the page regression * * is a LOB space and the regression * * results in a page type changing, a * * massive storage overlay may occur. * **************************************************************** * RECOMMENDATION: * **************************************************************** A timing window exists in which DB2 may fail to register a page for a GBP-dependent pageset, with the result that the member does not get cross-invalidated when another member updates the page, potentially resulting in broken data. The window only exits if the following conditions are met: - this member was the last to update the page before the object became non-GBP-dependent. - this same member was the first to update the page when the object became GBP-dependent again. - the page was still resident in the local buffer pool from the prior update. - the first update after becoming GBP-dependent again was to completely reformat the page. - the page gets written directly to DASD due to the page set being GBPCACHE NONE or GBPCACHE SYSTEM. If PM67544 (UK82633) is not installed, or if OA38419 (UA66420, UA66421) is not installed, or if the GBP is allocated in a CF with a CFLEVEL less than 17, then the page would have been implicitly cross-invalidated when the object went non-GBP-dependent, so no data integrity exposure would exist.
Problem conclusion
DB2 has been fixed to ensure that a page being reformatted is registered to the CF, regardless of whether it was previously registered during a prior period of GBP-dependency.
Temporary fix
********* * HIPER * *********
Comments
APAR Information
APAR number
PM82301
Reported component name
DB2 OS/390 & Z/
Reported component ID
5740XYR00
Reported release
A10
Status
CLOSED PER
PE
YesPE
HIPER
YesHIPER
Special Attention
NoSpecatt
Submitted date
2013-02-07
Closed date
2013-03-07
Last modified date
2013-04-15
APAR is sysrouted FROM one or more of the following:
APAR is sysrouted TO one or more of the following:
UK92353
Modules/Macros
DSNB1AGB DSNB1CMD DSNB1CNE DSNB1GC1 DSNB1GET DSNB1PMI DSNB5DEL DSNB5PCO
Fix information
Fixed component name
DB2 OS/390 & Z/
Fixed component ID
5740XYR00
Applicable component levels
RA10 PSY
UP
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Document Information
Modified date:
15 April 2013