I know about the Oracle SGA and PGA, but I also hear about a RAM
region called the User Global Area (UGA). What is the UGA and
how does it differ from the Program Global Area (PGA)?
Answer: For dedicated sessions, the UGA is a
part of the RAM heap in the PGA that controls user sessions space
for sorting and hash joins. If you are forced to use
shared servers (the Multi-threaded Server or MTS) the UGA is
inside the SGA large_pool_size region).
In sum, when using a dedicated connection, the User Global Area
(UGA) supplements the PGA with additional memory for the user's
session, such as private SQL areas and other session-specific
information such as sorting and session message queues.
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