Fixes are available
APAR status
Closed as program error.
Error description
When the DB2_REDUCED_OPTIMIZATION registry variable is set to NO_SORT_NLJOIN, the optimizer may still generate query plans that force sorts for nested loop joins (NLJN). Likewise, when the DB2_REDUCED_OPTIMIZATION registry variable is set to NO_SORT_MGJOIN, the optimizer may still generate query plans that force sorts for merge scan joins (MSJN). . The DB2 Information Center contains futher information about the DB2_REDUCED_OPTIMIZATION registry variable: http://publib.boulder.ibm.com/infocenter/db2luw/v9r5/index.jsp?t opic=/com.ibm.db2.luw.admin.regvars.doc/doc/r0005664.html . This problem does not occur if both NO_SORT_NLJOIN and NO_SORT_MGJOIN are set. .
Local fix
In order to workaround the problem, you can set the registry setting to both, eg: . db2set DB2_REDUCED_OPTIMIZATION=NO_SORT_NLJOIN,NO_SORT_MSJOIN . These types of sorts can be useful for improving performance. Care must be take when considering the use of the NO_SORT_NLJOIN and NO_SORT_MGJOIN options, as performance can be severely impacted.
Problem summary
When the DB2_REDUCED_OPTIMIZATION registry variable is set to NO_SORT_NLJOIN, the optimizer may still generate query plans that force sorts for nested loop joins (NLJN). Likewise, when the DB2_REDUCED_OPTIMIZATION registry variable is set to NO_SORT_MGJOIN, the optimizer may still generate query plans that force sorts for merge scan joins (MSJN). The DB2 Information Center contains futher information about the DB2_REDUCED_OPTIMIZATION registry variable: http://publib.boulder.ibm.com/infocenter/db2luw/v9r5/index.jsp?t opic=/com.ibm.db2.luw.admin.regvars.doc/doc/r0005664.html . This problem does not occur if both NO_SORT_NLJOIN and NO_SORT_MGJOIN are set.
Problem conclusion
apar: iz50527 module: engn_sqno fixed >= v91 fpk8
Temporary fix
In order to workaround the problem, you can set the registry setting to both, eg: . db2set DB2_REDUCED_OPTIMIZATION=NO_SORT_NLJOIN,NO_SORT_MSJOIN . These types of sorts can be useful for improving performance. Care must be take when considering the use of the NO_SORT_NLJOIN and NO_SORT_MGJOIN options, as performance can be severely impacted.
Comments
APAR Information
APAR number
IZ50527
Reported component name
DB2 UDB ESE SOL
Reported component ID
5765F4102
Reported release
910
Status
CLOSED PER
PE
NoPE
HIPER
NoHIPER
Special Attention
NoSpecatt
Submitted date
2009-05-01
Closed date
2009-12-02
Last modified date
2009-12-02
APAR is sysrouted FROM one or more of the following:
APAR is sysrouted TO one or more of the following:
Modules/Macros
ENG_SQNO
Fix information
Fixed component name
DB2 UDB ESE SOL
Fixed component ID
5765F4102
Applicable component levels
R910 PSN
UP
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Document Information
Modified date:
02 December 2009