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CPI4330 - &6 tasks used for parallel &10 scan of file &1. ( OS/400 )

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Message : CPI4330
&6 tasks used for parallel &10 scan of file &1.

Message Long Text :

Cause . . . . . : &6 is the average numbers of tasks used for a &10 scan of member &3 of file &1 in library &2.
If file &1 in library &2 is a logical file, then member &9 of physical file &7 in library &8 is the actual file from which records are being selected.
A file name starting with *QUERY or *N for the file indicates a temporary result file is being used.
The query optimizer has calculated that the optimal number of tasks is &5 which was limited for reason code &4. The reason code definitions are:
1 - The *NBRTASKS parameter value was specified for the DEGREE parameter of the CHGQRYA CL command.
2 - The optimizer calculated the number of tasks which would use all of the central processing units (CPU).
3 - The optimizer calculated the number of tasks which can efficiently run in this job's share of the memory pool.
4 - The optimizer calculated the number of tasks which can efficiently run using the entire memory pool.
5 - The optimizer limited the number of tasks to equal the number of disk units which contain the file's data.
The database manager may further limit the number of tasks used if the allocation of the file's data is not evenly distributed across disk units.
Recovery . . . : To disallow usage of parallel &10 scan, specify *NONE on the query attribute degree.
A larger number of tasks might further improve performance. The following actions based on the optimizer reason code might allow the optimizer to calculate a larger number:
1 - Specify a larger number of tasks value for the DEGREE parameter of the CHGQRYA CL command. Start with a value for number of tasks which is a slightly larger than &5.
2 - Simplify the query by reducing the number of fields being mapped to the result buffer or by removing expressions. Also, try specifying a number of tasks as described by reason code 1.
3 - Specify *MAX for the query attribute DEGREE.
4 - Increase the size of the memory pool.
5 - Use the CHGPF CL command or the SQL ALTER statement to redistribute the file's data across more disk units.
For more information, refer to the DB2 for i - Database Performance and Query Optimization topic collection in the Database category in the IBM i Information Center.
Technical description . . . . . . . . : Parallel &10 scan can only be implemented when the system feature DB2 Symmetric Multiprocessing is installed on the system.

Message File : QCPFMSG
Library Message File : QSYS2924


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