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The alternative is to
give each person an equal serving and wait for the slower eaters to finish.
Figure 7-5 illustrates the splitting of a set of blocks into ranges.
Parallelism for Tables and Partitions of Tables
With partitioned tables, introduced in Oracle8, an operation may involve one, some,
or all of the partitions of a partitioned table. There is essentially no difference in how
block-range parallelism dynamically splits the set of blocks to be read for a regular
table as opposed to a partitioned table. Once the optimizer has determined which
Figure 7-5. Dynamic block-range parallelism
PE
Process
PE
Process
Each
section is
a range of
blocks Result: Everyone eats all the time
One pie Served in helpings
172 | Chapter 7: Oracle Performance
partitions should be accessed for the operation, all the blocks of all partitions
involved are treated as a pool to be broken into ranges.
This assumption by the optimizer leads to a key consideration for using parallelism
and partitioned tables. The degree of parallelism (i.


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