The amount of free SGA memory available in the database

Question

Hi,
How can we calculate the amount of free SGA memory available from the instance if the database is not set for Memory management.If the sga_max_size is set for a particular value and the db_cache_size and the shared_pool and all other components are specified,how can one determine whether all the memory allocated for SGA is in use?

Answer 1

How can we calculate the amount of free SGA memory available from the instance if the database is not set for Memory management.When the SGA is allocated, the memory is fixed, and none of it is "free" really.
how can one determine whether all the memory allocated for SGA is in use? Are you asking about usage WITHIN the pools? If so, shortly after startup the database buffer and shared_pool will fill-up and stay full . . . . .
Here is the script that I use to see inside the data buffer contents:
set pages 999
set lines 80
spool blocks.lst
ttitle 'Contents of Data Buffers'
drop table t1;
create table t1 as
select
o.object_name object_name,
o.object_type object_type,
count(1) num_blocks
from
dba_objects o,
v$bh bh
where
o.object_id = bh.objd
and
o.owner not in ('SYS','SYSTEM')
group by
o.object_name,
o.object_type
order by
count(1) desc
column c1 heading "Object|Name" format a30
column c2 heading "Object|Type" format a12
column c3 heading "Number of|Blocks" format 999,999,999,999
column c4 heading "Percentage|of object|data blocks|in Buffer" format 999
select
object_name c1,
object_type c2,
num_blocks c3,
(num_blocks/decode(sum(blocks), 0, .001, sum(blocks)))*100 c4
from
t1,
dba_segments s
where
s.segment_name = t1.object_name
and
num_blocks > 10
group by
object_name,
object_type,
num_blocks
order by
num_blocks desc
Hope this helps. . ..
Don Burleson
Oracle Press author