SGA_TARGET again

I've read some about SGA_TARGET and SGA_MAX_SIZE, but
there are things I don't understand well I think.
1) SGA_MAX_SIZE is said to be for a life of an
instance -> But I can change it with alter system set
sga_max_size=... scope=spfile, restart the database
and it gets changed. Why?I'm sorry. Your question doesn;t make sense to me ...
perhaps the confusion is that 'the life of an instance' is from startup to shutdown ... restart and you have a new instance.
>
2) Why is exactly SGA_TARGET for? If it's set to a
non-zero value it's just to indicate we have ASMM
enabled? SGA_TARGET is written to set total memory
for SGA. But we can change it dynamically, up to
SGA_MAX_SIZE, that's why for me SGA_MAX_SIZE looks
rather for total memory for SGA. It can be changed
too though...MAX_SIZE is exactly that - the max size. The OS pre-allocates to the max size, BUT some OSs do not need to physically assign the memory that has been allocated. That allows the OS to have pointers to 'memory that needs to be allocated when it's needed'. So the process thinks it has MAX_SIZE available but it ain;t really there. See http://blog.tanelpoder.com/2007/08/28/operating-systems-are-lazy-allocating-memory/
TARGET is the amount that is allowed to be in use at a specific point in time. It is less than, or equal to MAX_SIZE. A description, including the impact on the auto-allocated sizes, is at http://download.oracle.com/docs/cd/B19306_01/server.102/b14237/initparams192.htm#sthref792
Therefore, on a 4 GB machine you can have 4 instances each with MAX_SIZE set to 3GB but TARGET set to 800M each. Then, when it's needed, you can back off some to increase one in particular without shutting any down simply by TARGET.
The really, really confusing part is that some OSs report that the memory is 'in use' simply because is allocated. That makes it appear that we have a problem.

Similar Messages

ALTER SYSTEM SET SGA_TARGET

Hi,
in 10g R2 should I stop/start database when I change sGA_TARGET :
ALTER SYSTEM SET SGA_TARGET=value [SCOPE={SPFILE|MEMORY|BOTH}]
Thank you.

user522961 wrote:
OK.
When I query V$PARAMETER I have the OLD value for SGA_TARGET. It is normal because the value in V$PARAMETER comes from starting and spfile. How can I be sur that now oRACLE uses the new value for SGA_TARGET effectively ?
Thanks again.Not sure I understand your question. If you set SGA_TARGET with SCOPE=MEMORY or BOTH, it should be in effect immediately.
SQL> alter system set sga_target=253M scope=both;
System altered.
SQL> select value bytes, value/1048576 MB from v$parameter where name = 'sga_target';
BYTES              MB
268435456         256
SQL> show parameter sga
NAME                                 TYPE        VALUE
lock_sga                             boolean     FALSE
pre_page_sga                         boolean     FALSE
sga_max_size                         big integer 512M
sga_target                           big integer 256M
SQL> alter system set sga_target=257M scope=both;
System altered.
SQL> select value bytes, value/1048576 MB from v$parameter where name = 'sga_target';
BYTES              MB
272629760         260
SQL> show parameter sga
NAME                                 TYPE        VALUE
lock_sga                             boolean     FALSE
pre_page_sga                         boolean     FALSE
sga_max_size                         big integer 512M
sga_target                           big integer 260M
SQL>

SGA_TARGET not Changing?

Hi Experts...
We use Oracle 10g R2(1002000300) on Hp-Unix for the Production & the OS RAM is 8GB
We had the SGA_MAX_SIZE as 1GB & SGA_TARGET also 1GB,
I have changed the SGA_MAX_SIZE to 3000M,
SQL>ALTER SYSTEM SET SGA_MAX_SIZE = 3000M SCOPE=SPFILE;
System altered.
then Shutdown the Database
SQL> shutdown immediate;
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> conn sys/orcl_2009_it as sysdba
Connected to an idle instance.
SQL> startup
ORACLE instance started.
Total System Global Area 3154116608 bytes
Fixed Size 2061600 bytes
Variable Size 2231372512 bytes
Database Buffers 905969664 bytes
Redo Buffers 14712832 bytes
Database mounted.
Database opened.
SQL> show parameter sga_max_size
NAME TYPE VALUE
sga_max_size big integer 3008M
SQL> ALTER SYSTEM SET SGA_TARGET = 2500M SCOPE=SPFILE;
System altered.
SQL> show parameter SGA_TARGET
NAME TYPE VALUE
sga_target big integer 1G
Again I Tried with Less Value
SQL> ALTER SYSTEM SET SGA_TARGET = 2000M SCOPE=SPFILE;
System altered.
But Still the SGA_TARGET Value Didnt Change
SQL> show parameter SGA_TARGET
NAME TYPE VALUE
sga_target big integer 1G
why this Strange Behaviour,it has to update the SGA_TARGET?
It didnt happen???
please Kindly Help me out in this
many thanks

Excellent...
Many thanks to Centinul,P. Forstmann ,asifkabir
On Restarting the Database
i find the SGA_TARGET New Assiggned Value 2500 M
SQL> shutdown immediate;
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup
ORACLE instance started.
Total System Global Area 3154116608 bytes
Fixed Size 2061600 bytes
Variable Size 687868640 bytes
Database Buffers 2449473536 bytes
Redo Buffers 14712832 bytes
Database mounted.
Database opened.
SQL> sho parameter sga_target
NAME TYPE VALUE
sga_target big integer 2512M
SQL>
Many thanks Experts for the Excellent Support
Have Great Time

ALTER SYSTEM SET SGA_TARGET = 0 scope=spfile; not working

SQL> ALTER SYSTEM SET SGA_TARGET = 0 scope=spfile;
System altered.
SQL> shutdown immediate;
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup;
ORACLE instance started.
Total System Global Area 2121256960 bytes
Fixed Size 2243280 bytes
Variable Size 1140852016 bytes
Database Buffers 973078528 bytes
Redo Buffers 5083136 bytes
Database mounted.
Database opened.
SQL> show parameters sga
NAME TYPE VALUE
lock_sga boolean FALSE
pre_page_sga boolean FALSE
sga_max_size big integer 2032M
sga_target big integer 0
SQL> create pfile=#/home/oracle/per03pfile' from spfile;
pfile has
*.sga_max_size=0
*.sga_target=0
and
instance1.__sga_target=2130706432
instance2.__sga_target=2130706432
tried ALTER SYSTEM SET SGA_TARGET = 0 scope=spfile sid='*'; aswell ...
oracle v11.2.0.2
GI 11.2.0.2
linux 64 bit

Chinar wrote:
user9198889 wrote:
SQL> ALTER SYSTEM SET SGA_TARGET = 0 scope=spfile;
System altered.
SQL> shutdown immediate;
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup;
ORACLE instance started.
Total System Global Area 2121256960 bytes
Fixed Size 2243280 bytes
Variable Size 1140852016 bytes
Database Buffers 973078528 bytes
Redo Buffers 5083136 bytes
Database mounted.
Database opened.
SQL> show parameters sga
NAME TYPE VALUE
lock_sga boolean FALSE
pre_page_sga boolean FALSE
sga_max_size big integer 2032M
sga_target big integer 0
SQL> create pfile=#/home/oracle/per03pfile' from spfile;
pfile has
*.sga_max_size=0
*.sga_target=0
and
instance1.__sga_target=2130706432
instance2.__sga_target=2130706432
tried ALTER SYSTEM SET SGA_TARGET = 0 scope=spfile sid='*'; aswell ...
oracle v11.2.0.2
GI 11.2.0.2
linux 64 bitWhile SGA_MA_SIZE <> 0 then it seems SHARED MEMORY constructed according this setting.So it is not recommended to avoid automatic shared memory management.But if you decide this then you have to identify SHARED_PLOOL_SIZE,DB_CACHE_SIZE(in additionally LOG_BUFFER and LARGE_POOL) parameter manually and
ALTER SYSTEM SET SGA_TARGET=o scope=spfile and ALTER SYSTEM SET SGA_MAX_SIZE=o scope=spfile and restart database again.SQL> alter system set sga_max_size=0 scope=spfile sid='instance1';
System altered.
SQL> shutdown immediate;
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup;
ORACLE instance started.
SQL> show parameters sga
NAME TYPE VALUE
lock_sga boolean FALSE
pre_page_sga boolean FALSE
sga_max_size big integer 2032M
sga_target big integer 0
SQL>
has it got todo with AMM being enabbled?

For sga_target

we are using 11G DB. our database sga_target = 0.so we can assume that ASSM is disbled. what wud be the oracle recomended size of enable ASSM. where as sga_max_size = 3054M.
also what is the utlity of ASSM in 11G.how can we check?
thanks in advance..

please go thorugh our DB reading of those views.
SQL> select * from v$memory_target_advice;
MEMORY_SIZE MEMORY_SIZE_FACTOR ESTD_DB_TIME ESTD_DB_TIME_FACTOR    VERSION
        876                .25          696              1.0006          0
       1752                 .5          696                   1          0
       2628                .75          696                   1          0
       3504                  1          696                   1          0
       4380               1.25          696                   1          0
       5256                1.5          696                   1          0
       6132               1.75          696                   1          0
       7008                  2          696                   1          0
8 rows selected.
SGA_SIZE SGA_SIZE_FACTOR ESTD_DB_TIME ESTD_DB_TIME_FACTOR ESTD_PHYSICAL_READS
       572             .25          899              1.2935              218739
      1144              .5          708              1.0187              108602
      1716             .75          695                   1               97708
      2288               1          695                   1               97708
      2860            1.25          695                   1               97708
      3432             1.5          695                   1               97708
      4004            1.75          695                   1               97708
      4576               2          695                   1               97708
8 rows selected.Now please suggest......
Thanks once again..
Edited by: piku on Feb 16, 2011 9:16 PM

Performance Problem Again

Hi all,
We are encountering performance problem again
The batch process deletes 1M rows every night which took 30mins the usual.
But last night (12AM) it took more that 2hrs and hangs.
Does it help if I run gather_schena stats regularly when there is constant DELETE on the table?
Please help me check our ASH, AWR, ADDM to resolve the issue.
ADDM
https://app.box.com/s/7o734e70aa2m2zg087hf
ASH
https://app.box.com/s/xadlxfk0r5y7jvtxfsz7
AWR
https://app.box.com/s/x8ordka2gcc6ibxatvld
Thanks....
zxy

Hi ARM,
***What is the SGA_TARGET or MEMORY_TARGET that the database is running on?
Our server has 8Gb Physical Memory and 8Gb Swap.
What is the ideal SGA_TARGET and MEMORY_TARGET shouldbe?
Our current setting is:
========
SQL> show parameter memory
NAME                                 TYPE        VALUE
hi_shared_memory_address             integer     0
memory_max_target                        big integer 5936M
memory_target                                big integer 5936M
shared_memory_address                 integer     0
SQL> show parameter sga_
NAME                                 TYPE        VALUE
sga_max_size                         big integer 5936M
sga_target                               big integer 0
Thanks

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when i login on game center it say enter your birth date when i enter it and i perss next the birth day will come again and again what should do

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HT4972 After syncing my iPad2 to iTunes, I can't get it to work again.

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Itunes wont open. Ive tried uninstalling, cleaned up my PC and then re installed again but still wont open! There are no error messages. It just wont open

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http://support.apple.com/kb/ts1717
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Sheila M.

How long does it take for the warehouse to show a phone as recieved so I can pay my final bill? I would like to sign up for Verizon again as I am very unsatisfied with my new company but cannot until this is resolved.

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How recently did you switch? If it's less than 60 days, then Verizon simply reinstates your previous account. The fact that you were on the EDGE plan and mailed the devices back, and they apparently are somewhere in the system, could cause complications, and it might just work out that you just go back on the same plan and they set you up with the same devices. I'm not sure how it will go - but since you are still being billed for the devices...

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Your webpages/tabs are still there. When you start firefox again, there is a "Restore Previous Session" icon below. If you click that, it will open up all your tabs again.
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Mail applications is blank when I open it, then it closes and opens again by itself, keeping blank

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rjliii wrote:
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[https://www.mozilla.org/en-US/firefox/new/ Firefox]
[http://kb.mozillazine.org/Installation_directory Installation Folder]
[http://kb.mozillazine.org/Profile_folder Profile Folder]
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SGA_TARGET again

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