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DB2 - Problem description

Problem IC66653 Status: Closed

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

product:
DB2 FOR LUW / DB2FORLUW / 980 - 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 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. 
* 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. 
* 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. 
* 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. 
* 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).                          * 
**************************************************************** 
* RECOMMENDATION:                                              * 
* Upgrade to DB2 version 9.8 fix pack 3                        * 
****************************************************************
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 9.8 Fix Pack 3 for Linux, UNIX, and Windows
DB2 Version 9.8 Fix Pack 4 for AIX and Linux
DB2 Version 9.8 Fix Pack 5 for AIX and Linux

Solution
First fixed in DB2 version 9.8 fix pack 3
Workaround
not known / see Local fix
Timestamps
Date  - problem reported    :
Date  - problem closed      :
Date  - last modified       :
24.02.2010
20.12.2010
20.12.2010
Problem solved at the following versions (IBM BugInfos)
9.8.FP3
Problem solved according to the fixlist(s) of the following version(s)
9.8.0.3 FixList
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