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DB2 - Problem description

Problem IC66252 Status: Closed

DB2 INSTANCE ENDS ABNORMALLY COMPILING QUERY WITH A LARGE NUMBER OF UNIONS

product:
DB2 FOR LUW / DB2FORLUW / 950 - DB2
Problem description:
Compiling a query with a large number of UNIONs may result in a 
stack overflow and termination of the DB2 instance.  The call 
stack looks similar to this example from Linux: 
 
  0000002A97833854 _Z24sqlnq_process_connect_byP9sqlnq_qtbP3loc 
+ 0x001c 
 
(/ms/dist/ibmdb2/PROJ/ds/9.5.4.4/.exec/x86_64.linux.2.6.glibc.2. 
3/lib64/libdb2e.so.1) 
  0000002A97835D77 _Z24sqlnq_process_connect_byP9sqlnq_qtbP3loc 
+ 0x253f 
 
(/ms/dist/ibmdb2/PROJ/ds/9.5.4.4/.exec/x86_64.linux.2.6.glibc.2. 
3/lib64/libdb2e.so.1) 
   0000002A97835D77 _Z24sqlnq_process_connect_byP9sqlnq_qtbP3loc 
+ 0x253f 
 
(/ms/dist/ibmdb2/PROJ/ds/9.5.4.4/.exec/x86_64.linux.2.6.glibc.2. 
3/lib64/libdb2e.so.1) 
  0000002A97835D77 _Z24sqlnq_process_connect_byP9sqlnq_qtbP3loc 
+ 0x253f 
 
(/ms/dist/ibmdb2/PROJ/ds/9.5.4.4/.exec/x86_64.linux.2.6.glibc.2. 
3/lib64/libdb2e.so.1) 
  ... 
 
For this problem to occur, the DB2_COMPATIBILITY_VECTOR registry 
variable must have the hierarchical query bit set (bit 4), e.g.: 
 
  DB2_COMPATIBILITY_VECTOR=08 
 
or 
 
  DB2_COMPATIBILITY_VECTOR=ORA 
 
But the query does not necessarily have to use hierarchical 
queries (i.e. a CONNECT BY clause).
Problem Summary:
**************************************************************** 
* USERS AFFECTED:                                              * 
* ALL                                                          * 
**************************************************************** 
* PROBLEM DESCRIPTION:                                         * 
* Compiling a query with a large number of UNIONs may resultin * 
* astack overflow and termination of the DB2 instance.         * 
* Thecallstack looks similar to this example from              * 
* Linux:0000002A97833854_Z24sqlnq_process_connect_byP9sqlnq_qtbP 
* 0x001c(/ms/dist/ibmdb2/PROJ/ds/9.5.4.4/.exec/x86_64.linux.2.6. 
* 0x253f(/ms/dist/ibmdb2/PROJ/ds/9.5.4.4/.exec/x86_64.linux.2.6. 
* 0x253f(/ms/dist/ibmdb2/PROJ/ds/9.5.4.4/.exec/x86_64.linux.2.6. 
* 0x253f(/ms/dist/ibmdb2/PROJ/ds/9.5.4.4/.exec/x86_64.linux.2.6. 
* this problem to occur, the                                   * 
* DB2_COMPATIBILITY_VECTORregistryvariable must have the       * 
* hierarchical query bit set (bit                              * 
* 4),e.g.:DB2_COMPATIBILITY_VECTOR=08orDB2_COMPATIBILITY_VECTOR= 
* the query does not necessarily have to use                   * 
* hierarchicalqueries (i.e. a CONNECT BY clause).              * 
**************************************************************** 
* RECOMMENDATION:                                              * 
* Upgrade to DB2 v9.5 Fix Pack 6Otherwise, disable             * 
* hierarchical queries if not needed byunsetting bit 4         * 
* inDB2_COMPATIBILITY_VECTOR.  Alternatively, rewrite the      * 
* querytoreduce the number of UNIONs.                          * 
****************************************************************
Local Fix:
Disable hierarchical queries if not needed by unsetting bit 4 in 
DB2_COMPATIBILITY_VECTOR.  Alternatively, rewrite the query to 
reduce the number of UNIONs.
available fix packs:
DB2 Version 9.5 Fix Pack 6a for Linux, UNIX, and Windows
DB2 Version 9.5 Fix Pack 7 for Linux, UNIX, and Windows
DB2 Version 9.5 Fix Pack 8 for Linux, UNIX, and Windows
DB2 Version 9.5 Fix Pack 9 for Linux, UNIX, and Windows
DB2 Version 9.5 Fix Pack 10 for Linux, UNIX, and Windows

Solution
First fixed in DB2 v9.5 Fix Pack 6
Workaround
not known / see Local fix
BUG-Tracking
forerunner  : APAR is sysrouted TO one or more of the following: IC66378 IC66653 
follow-up : 
Timestamps
Date  - problem reported    :
Date  - problem closed      :
Date  - last modified       :
11.02.2010
25.05.2010
25.05.2010
Problem solved at the following versions (IBM BugInfos)
9.5.FP6,
9.5.FP6Other
Problem solved according to the fixlist(s) of the following version(s)
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