Oracle can further determine the degree of parallelism based on parameters set
in the initialization file or using the adaptive degree of parallelism feature, described
in Chapter 7. This adaptive multiuser feature makes use of algorithms that take into
account the number of threads. Additional tuning parameters can also affect parallelism,
although the need for tuning of such parameters is much diminished in recent
Oracle releases.
Symmetric Multiprocessing Systems
One of the early limiting factors for a uniprocessor system was the ultimate speed of
its processor??”all applications have to share this one resource. Symmetric Multiprocessing
(SMP) systems were invented in an effort to overcome this limitation by
adding CPUs to the memory bus, as shown in Figure 12-2.
Figure 12-2. Typical Symmetric Multiprocessing (SMP) system
Disk
Memory
I/O
CPU with L1 Cache
L2 Cache
CPU with L1 Cache
L2 Cache
294 | Chapter 12: Oracle and Hardware Architecture
Each CPU has its own memory cache. Data resident in the cache of one CPU is
sometimes needed for processing by a second CPU.
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