Size of the fixed SGA
The size of the fixed SGA does not change. This is probably the reason that the fixed SGA is called fixed.
The size of the fixed SGA can be queried like so:
select
value
from
v$sga
where
name = 'Fixed Size';
Accessing fixed SGA memory with x$ksmmem
The
fixed (x$) table x$ksmmem allows to query each address aligned on 8 byte boundaries of the fixed SGA. Thus, the size of the fixed SGA is equal to:
select
8 * count(*) -- 8 bytes per record on 64 bit matchins
from
x$ksmmem;
Of course, the same value is also obtained with
select
max(to_number(x$ksmmem.addr, lpad('X', 16, 'X'))) -
min(to_number(x$ksmmem.addr, lpad('X', 16, 'X'))) + 8
from
x$ksmmem;