Saturday, 24 August 2013

DB2 Sort Pool

At startup, DB2 allocates a sort pool in the private area of the DBM1 address space. DB2 uses a special sorting technique, called a tournament sort. 
During the sorting processes, this algorithm commonly produces logical work files called runs, which are intermediate sets of ordered data. If the sort pool is large enough, the sort completes in that area. 
More often than not, the sort cannot complete in the sort pool, and the runs are moved into the DSNDB07 work files that are used to perform sorts. These runs are later merged to complete the sort. 
When DSNDB07 is used for holding the pages that make up the sort runs, you could experience performance degradation if the pages get externalized to the physical work files, as they will have to be read back in later in order to complete the sort.

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