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Problem IT20463
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Status: Closed |
INCORRECT RESULTS ARE POSSIBLE WHEN CONCURRENT QUERIES ACCESS COLUMNAR ORGANIZED TABLES AND USE CS ISOLATION |
| product: |
DB2 FOR LUW / DB2FORLUW / B10 - DB2 |
| Problem description: |
Concurrency issues can arise if updates to entries are committed
before other queries fetch data from CDE; this results in rows
that originally matched the query being returned with updated
values when they should not have been selected.
Example:
1) Session 1 executes an update to an entry but does not
commit the work: UPDATE t1 SET COL1 = 9 WHERE COL1 = 8
2) Session 2 executes a select query: SELECT * FROM t1 WHERE
col1=8 with CS
DB2 returns an FETCH-ISCAN access plan. The runtime has not
started the ISCAN operation yet.
3) Session 1 commits the work for the UPDATE, which means
that we should not have any entries where COL1 = 8
4) Session 2 completes its execution of the FAST FETCH-ISCAN
plan and returns rows where COL1 = 9 when they were previously
COL1 = 8, which is not expected.
The ISCAN operator returns pseudo deleted keys, which have rows
that have COL1=8 (because the UPDATE has not been committed
yet). When DB2 fetches columns from CDE tables with TSN
corresponding to tuples with the old COL1 = 8, the original
index predicate (WHERE COL1 = 8) was not being reapplied. As a
result, these tuples were incorrectly returned when in fact
their updated values are now 9. |
| Problem Summary: |
****************************************************************
* USERS AFFECTED: *
* CDE environments *
****************************************************************
* PROBLEM DESCRIPTION: *
* See Error Description *
****************************************************************
* RECOMMENDATION: *
* Upgrade to the latest fix pack. *
**************************************************************** |
| Local Fix: |
|
| available fix packs: |
DB2 Version 11.1 Mod 2 Fix Pack 2 for Linux, UNIX, and Windows
Db2 Version 11.1 Mod2 Fix Pack2 iFix001 for Linux, UNIX, and Windows
Db2 Version 11.1 Mod2 Fix Pack2 iFix002 for Linux, UNIX, and Windows
Db2 Version 11.1 Mod 3 Fix Pack 3 for Linux, UNIX, and Windows
Db2 Version 11.1 Mod3 Fix Pack3 iFix001 for Linux, UNIX, and Windows
Db2 Version 11.1 Mod3 Fix Pack3 iFix002 for Linux, UNIX, and Windows
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| Solution |
Problem was first fixed in DB2 UDB Version 11.1 fix pack 2. |
| Workaround |
not known / see Local fix |
| Timestamps |
Date - problem reported :
Date - problem closed :
Date - last modified :
| 04.05.2017
23.06.2017
23.06.2017 |
| Problem solved at the following versions (IBM BugInfos) |
|
| Problem solved according to the fixlist(s) of the following version(s) |
