sga_target to a non zero value enables automatic shared memory management and specifies the size of SGA. sga_target > 0, the following pools are automatically sized: db_cache_size)
shared_pool_size)
large_pool_size)
java_pool_size)
streams_pool_size)
data_transfer_cache_size) sga_target: keep, recycle and other block sizes
select
sga_size,
sga_target,
sga_size - sga_target diff
from (
select
(select sum (value) from v$sga ) sga_size,
(select to_number(value) from v$parameter where name = 'sga_target') sga_target
from
dual
);
sga_target with the following query: select ( (select sum(value ) from v$sga ) - (select current_size from v$sga_dynamic_free_memory) ) "sga_target" from dual;
sga_target, it must be smaller than sga_max_size (otherwise an ORA-02097: parameter cannot be modified because specified value is invalid combined with ORA-56747 is thrown).