Databases Reference
In-Depth Information
Figure 12-1. Typical Symmetric Multiprocessing (SMP) node
Each CPU has its own memory cache. Data resident in the cache of one CPU is some‐
times needed for processing by a second CPU. Because of this potential sharing of data,
the CPUs for such machines must be able to “snoop” the memory bus to determine
where copies of data reside and whether the data is being updated. This snooping is
managed transparently by the operating system that controls the SMP system. Oracle
Standard Edition One, Standard Edition, or Enterprise Edition can be used on these
platforms. SMP platforms have been available since the 1980s as midrange systems,
primarily as Unix-based machines. Today, the most popular operating systems in this
category are Linux and Windows variations, though Solaris, AIX, and HP-UX also re‐
main popular. High-end systems and nodes feature CPUs containing high numbers of
cores, larger L2 cache, a faster memory bus, and/or multiple higher-speed I/O channels.
Each enhancement is intended to remove potential bottlenecks that can limit
performance.
The number of CPUs possible in an SMP system or node is limited by scalability of the
system (memory) bus. As more CPUs are added to the bus, the bus itself can become
saturated with traffic between CPUs attached to the bus. Memory itself can now scale
into the terabytes (TBs) on such systems.
