Search notes:

Oracle: Init parameters SGA_MAX_SIZE and SGA_MIN_SIZE

The value of sga_max_size specifies the maximum size for the SGA for the lifetime of the instance.
When Oracle starts up, it reserves («allocates») as much virtual (not physical) memory as specified with sga_max_size in order to make sure this amount of memory can be provided to processes that need memory.
If the size of sga_max_size is larger than the sum of configured size for SGA components, the remaining memory is found/seen in the variable SGA.
The default value of sga_max_size depends on the values of memory_target and memory_max_target.
sga_max_size should not be set if memory_target is set.

TODO

Are the following two numbers not equal because sum(value) from v$sga is not rounded up to a granule size? (See MOS note 266702.1)
select to_number(value) from v$parameter where name = 'sga_max_size' union all
select sum(value) from v$sga;

See also

MOS note 260171.1
init parameters such as sga_target and memory_target.

Index

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