Modifying Parameters for Automatically Managed Components (104)

When SGA_TARGET is not set,
the automatic shared memory management feature is not enabled. Therefore the rules
governing resize for all component parameters are the same as in earlier releases.
However, when automatic shared memory management is enabled, the manually
specified sizes of automatically sized components serve as a lower bound for the size
of the components. You can modify this limit dynamically by changing the values of
the corresponding parameters.

If the specified lower limit for the size of a given SGA component is less than its
current size, there is no immediate change in the size of that component. The new
setting only limits the automatic tuning algorithm to that reduced minimum size in the
future. For example, consider the following configuration:
■ SGA_TARGET = 512M
■ LARGE_POOL_SIZE = 256M
■ Current actual large pool size = 284M

In this example, if you increase the value of LARGE_POOL_SIZE to a value greater
than the actual current size of the component, the system expands the component to
accommodate the increased minimum size. For example, if you increase the value of
LARGE_POOL_SIZE to 300M, then the system increases the large pool incrementally
until it reaches 300M. This resizing occurs at the expense of one or more automatically
tuned components.

If you decrease the value of LARGE_POOL_SIZE to 200, there is no immediate change
in the size of that component. The new setting only limits the reduction of the large
pool size to 200 M in the future.

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