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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