Sga_max_size & memory_max_target

Hi All,
Could you please tell me ...
In oracle 11.1 If I want to set Memory Parameter
alter system set memory_max_target=2000M scope=spfile;
alter system set memory_target=2000M scope=spfile;
Do I need to set sga_max_size value ? or it will set automatically
As Per my knowledge
We need to Set following sga parameter to 0, if ASMM, or AMM set to ON.(By default oracle 11g using ASMM, or AMM set to ON)
alter system set sga_target=0 scope=spfile;
alter system set pga_aggregate_target=0 scope=spfile;
I am not sure about sga_max_size
Thanking in Advance
Dev

Dev wrote:
I tested setting of SGA_MAX_SIZE=0 it is not setting to 0 after restart but not setting to 0
alter system set SGA_MAX_SIZE =0 scope=spfile
and bounced the instance
ALTER SYSTEM SET SGA_TARGET = 0 scope=spfile; not working
Have you allocated manually for each Memory parameters? DB Buffer cache, shared pool & so on?
If you are setting to ZERO means, you are configuring remaining all parameter manually.
Set those values and then try to set SGA_MAX to 0 then bounce it.

Similar Messages

Memory_max_target and memory_target on 11.2

Hi gurus,
after an upgrade from DBMS10g to 11.2 our DBA changed manually parameters about memory in the following way:
*.db_cache_size=2113929216
*.hash_area_size=101310720
*.java_pool_size=83886080
*.log_buffer=5097152
*.memory_target=0
*.pga_aggregate_target=838860800
*.sga_max_size=12884901888
*.sga_target=0
*.shared_pool_reserved_size=61331648
*.shared_pool_size=1677721600
Is this the right way to configuree parameters on 11g? or is better to set only the .memory_max_target and memory_target and allow Oracle to manage dynamically the other memory size?
Thanks in advance.

Hi DDF,
It is simple to use SGA_TARGET with SGA_MAX_SIZE (Need to allocate PGA) or Memory_target witn memory_max_target (not need to define PGA).
But make sure your applications are running ok with that setup. Sometimes you may need to define other memory parameters.
Cheers
M

Setting sga_max_size and memory_target

what happens when i set
sga_max_size = 4500
memory_target = 5000M
memory_max_target=5000M
sga_target=0
can / will oracle use more than 4.5GB for sga ?
can pga grow more than 500M ?
startup;
ORACLE instance started.
Total System Global Area 4710043648 bytes
Fixed Size 2234376 bytes
Variable Size 3925870584 bytes
Database Buffers 771751936 bytes
Redo Buffers 10186752 byt

user9198889 wrote:
g777 wrote:
hi
DB and OS version would be nice to see...
look here
http://www.dba-oracle.com/oracle11g/oracle_11g_memory_target_parameter.htm
SGA_MAX_SIZE & SGA_TARGET
linux 5.5
db 11.2.0.2 rac GI 11.2.0.2thanks for the links,
"When using AMM (by setting memory_target, and/or sga_target, the values for the “traditional” pool parameters (db_cache_size, shared_pool_size, &c) are not ignored. Rather, they will specify the minimum size that Oracle will always maintain for each sub-area in the SGA.
so that means PGA wont grow more than 500MB and SGA be set to minimum of 4.5GB?
actually if you carefully read the above comment it doesnt mentiond sga_max_size it only says traditional pools such as db_cache_size etc...
does this also include sga_max_size?
I had a look at the other link to a thread but the question is slightly diffrent, they are discussing relation of sga_target to memory_target, I am intrested to know about sga_nax_size inrelation to memory_target

SGA_MAX_SIZE and AMM

Hi, all,
I've been testing using AMM in our newly-upgraded 11gR2 databases. All databases (Prod and non-Prod) are running 11.2.0.3 on AIX 5.3 (64-bit).
I noticed that despite me explicitly setting the following to 0:
alter system set db_cache_size = 0 scope=spfile;
alter system set log_buffer = 0 scope=spfile;
alter system set pga_aggregate_target = 0 scope=spfile;
alter system set sga_max_size = 0 scope=spfile;
alter system set sga_target = 0 scope=spfile;
alter system set shared_pool_size = 0 scope=spfile;
alter system set shared_pool_reserved_size = 0 scope=spfile;
And allowing Oracle 'full control' how it manages all parts of the memory (SGA and PGA)
-- The 'big' database
alter system set memory_max_target = 24G scope=spfile;
alter system set memory_target = 24G scope=spfile;
-- The 'small' database
alter system set memory_max_target = 3G scope=spfile;
alter system set memory_target = 3G scope=spfile;
I bounce both databases and things seem to come up OK. The only exception is that sga_max_size seems to be set to a specific value:
For the 'big' database, it's 16Gb (2/3rds of the total memory_target)
For the 'small' database, it's 1536Mb (1/2 of the total memory_target)
I don't really understand why this is happening. I've double-checked my SPFILE, I've queried v$spparameter and I've read MOS 443746.1
+"If MEMORY_TARGET is set to a non-zero value:+
+If neither is set, they will be auto-tuned without any minimum or default values. We will have a policy of distributing the total memory set by MEMORY_TARGET parameter in a fixed ratio to the the SGA and PGA during initialization. The policy is to give 60% to the SGA and 40% to the PGA at startup."+
BUT I presume that sga_max_size works in the same way that it did when we weren't using AMM - it's the upper limit of the SGA. Not ideal, to be honest, as I can definitely see times when the SGA needs a LOT of buffer cache in Production (and, therefore, lots of SGA)
I do see this in the alert.logs whenever I restart the system:
Using parameter settings in server-side spfile /opt/oracle/product/11.2.0.3/db/dbs/spfilebigdb.ora
System parameters with non-default values:
processes                = 600
sessions                 = 928
timed_statistics         = TRUE
resource_limit           = TRUE
event                    = "10262 trace name context forever, level 160000"
sga_max_size             = 16G
So it's suggesting that it's querying the SPFILE and determining that sga_max_size should be set. But I've double-double-checked and that isn't the case.
Now, I know I can get around this by explicitly setting sga_max_size at memory_target. But I was wondering if anyone else had seen this before too?
Mark

Another workaround is to remove the memory components entirely from the SPFILE (instead of having them set to 0, don't have them in the file at all). This seems to also set the sga_max_size to the memory_target - which is expected behaviour given the MOS note.

Sga_max_size and sga_target values

I have an 11g database on windows with 4GB RAM, I have set the MEMORY_MAX_TARGET and MEMORY_TARGET, what should I do with the pre-existing sga_max_size and sga_target values

memory_target = sga_target + max(pga_aggregate_target, maximum PGA allocated)
MEMORY_MAX_TARGET = sum of the SGA and instance PGA sizes.
For Automatic memory management
set
ALTER SYSTEM SET SGA_TARGET = 0;
ALTER SYSTEM SET PGA_AGGREGATE_TARGET = 0;
Note:
In a text initialization parameter file, if you omit the line for MEMORY_MAX_TARGET and include a value for MEMORY_TARGET, the database automatically sets MEMORY_MAX_TARGET to the value of MEMORY_TARGET. If you omit the line for MEMORY_TARGET and include a value for MEMORY_MAX_TARGET, the MEMORY_TARGET parameter defaults to zero. After startup, you can then dynamically change MEMORY_TARGET to a nonzero value, provided that it does not exceed the value of MEMORY_MAX_TARGET.
Note:
The preceding steps instruct you to set SGA_TARGET and PGA_AGGREGATE_TARGET to zero so that the sizes of the SGA and instance PGA are tuned up and down as required, without restrictions. You can omit the statements that set these parameter values to zero and leave either or both of the values as positive numbers. In this case, the values act as minimum values for the sizes of the SGA or instance PGA.
Reference

11g sga_max_size

Hello,
Oracle 11 on Windows
In my parameter file the is no memory parameter, except MEMORY_TARGET.
If I set MEMORY_TARGET=250M, the sga_max_size is set (autom.) to 250M. Windows Taskmanager shows: Mem. uage=250M, VM Size=250M
If I set MEMORY_TARGET=1000M, the sga_max_size is set (autom.) to about 680M. Windows Taskmanager shows: Mem. uage=250M, VM Size=680M
It looks to me, that Oracle is determining a good 'starting point'. As far as I understand, the SGA will shrink when PGAs need memory and the sum of memory comes above MEMORY_TARGET. Will Oracle adjust the sga_max_size at that moment? In other words: is there a background process periodically controlling the total sga memory for Oracle (let it grow or shrink) according the the value of sga_max_size at that moment?
Thanks, Stephan

When either MEMORY_TARGET or MEMORY_MAX_TARGET is enabled, SGA_MAX_SIZE default value is set to the larger of the two specified parameters on non-Windows 32-bit operating system. On Windows 32-bit operating system, due to address space pressure, the default value of SGA_MAX_SIZE is calculated based on the total available virtual address space along with MEMORY_TARGET and MEMORY_MAX_TARGET.
To calculate the value on Windows 32-bit, SGA_MAX_SIZE larger of:
60% of MEMORY_TARGET if set and
60% of MEMORY_MAX_TARGET if set and
25% of total available virtual address space
http://docs.oracle.com/cd/B28359_01/readmes.111/b28280/toc.htm
Similar discussion has been done on below link :
What if I set MEMORY_MAX_TARGET and SGA_MAX_SIZE both?
Regards
Girish Sharma

Am I understanding SGA_TARGET and SGA_MAX_SIZE correctly?

Let's say I set SGA_MAX_SIZE to 1024MB and SGA_TARGET to 512MB.
As I understand it, this means that the total SGA size will never exceed 1024MB (that's the "hard cap"). Oracle will try to keep things around 512MB, but may burst up to 1024MB as needed.
Is that correct? Otherwise, I don't see the point of SGA_MAX_SIZE vs. SGA_TARGET.
BTW...I know MEMORY_TARGET and MEMORY_MAX_TARGET are the new 11g params, but Oracle ships XE with those turned off and the 10g SGA_* params and PGA_AGGREGATE_TARGET set...?

Hi,
In Oracle 11g MEMORY_TARGET is for automatic SGA and PGA management.MEMORY_MAX_SIZE is the maximum size to which your MEMORY_TARGET can be allocated.As shown below:
SQL> show parameter %MEMORY%
NAME TYPE VALUE
hi_shared_memory_address integer 0
memory_max_target big integer 1G
memory_target big integer 1G
But,When it comes to managing various other memory component like shared_pool,large_pool,Db_buffer_cache,log_buffer_cache,java_pool we still have to manage SGA_TARGET.
SQL> show parameter %SGA%
NAME TYPE VALUE
lock_sga boolean FALSE
pre_page_sga boolean FALSE
sga_max_size big integer 1G
sga_target big integer 0
Best regards,
Rafi.
http://rafioracledba.blogspot.com/
Edited by: Rafi (Oracle DBA) on Jun 22, 2011 11:54 PM

SGA_MAX_SIZE and SGA_TARGET in Oracle 10G

We have the following H/W with Solaris 9
SPARC-IV 16 CPUs
32GB RAM
128GB swap
What is the optimal size of sga_target and sga_max_size that can be configured for a heavy batch processing oracle server. Nothing runs except oracle in the above server.
We have currently 3GB SGA size , however our heavy queries are very slow.
We have huge updates on tables with more than 200Millions rows.
Do we need to have JAVA_POOL if the java stored procedure are NOT used.
However we are connecting to this database using JDBC also.
Moreover ASM is enabled in this server.
You expert suggetions are always welcome.

That's not a question that can be answered easily. It depends very much on where the time is going. Three main targets:
Writing the log file - which is largely about use of disks, not memory.
Reading data - lots of single block reads suggest looking at a bigger cache
Reading and writing temp because of large sorts/hash joins - pga configuration
One difficulty with TEMP is that the I/Os are often asynchronous, so a session can do a lot of TEMP I/O without recording much time - which means it can cause a problem elsewhere without suffering a problem itself.
You didn't mention the pga_aggregate_size - which is an important consideration in 10g and can be more important than the sga sizing in DSS and batch-like processing. Between them, the SGA and PGA_aggregate_target should probably account for a very large fraction of your memory - but (since you are on Solaris) make sure you look into large memory pages and intimate shared memory, otherwise you may need to leave a lot of memory available for the O/S memory management mechanisms.
As far as the java pool is concerned, check v$sgastat for pools which constantly show free memory, and reclaim any large free volumes.
Bottom line - if you've got the memory in the box, you might as well use it in the best possible place; but at the moment we don't have enough information to tell us where it would be most useful.
Regards
Jonathan Lewis
http://jonathanlewis.wordpress.com
http://www.jlcomp.demon.co.uk

Difference between SGA_MAX_SIZE and SGA_TARGET

Difference between SGA_MAX_SIZE and SGA_TARGET

user8645026 wrote:
Difference between SGA_MAX_SIZE and SGA_TARGETIs discussed in the database forum, not the forum for which the title is " Community Feedback and Suggestions (Do Not Post Product-Related Questions Here)".
Is also discussed in the documentation at http://tahiti.oracle.com

Increasing SGA_MAX_SIZE in Oracle 10.2.0.1

Hi,
we have successfully upgrade our database from 8.1.7.0 to 10.2.0.1
now in the database control, SGA max size is 524MB
i want to increase it, as to increase the size of SHARED_POOL_SIZE and DATBASE_BUFFER size
i have checked the init.ora file, in that there is no parameter mentioned as sga_max_size
from where and how to increase the SGA_MAX_SIZE in 10g version ?
with regards

Hi,
Database is using init.ora file in the pfile folder
In the init.ora file i have increased the SGA_MAX_SIZE parameter to 1024Mb from 524Mb
Now, from dbcontrol screen, Automatic Shared Memory Managment is Disabled and i want to make it ENABLE
now when i click on ENABLE button, on the next page it shows total SGa size i.e 332 Mb
and further wheni click on "OK" button for ASSM configuration, it shows the error as below :-
1.) SGATargetSize - ORA-02097 : parameter cannot be modified because specified vale is invalid ORA : cannot set sga_target due to existing internal settings, see alert log for information
in the alert log , it mentions
Cannot set sga_target with db_block_buffers set
and
Alter system set java_pool_size='0' SCOPE=MEMORY;
2) sharedPoolsize - ORA-02097 parameter cannot be modified because specified value is invalid ORA-04034: unable to shrink pool to specified size
now i just mentioned the memory component details for reference :
shared pool : 104 Mb
buffer cache : 169 Mb
large pool : 0
java pool : 4 Mb
other : 54 Mb
total SGA -- 332 Mb
Maximum SGA Size -- 1024 Mb
how to make ASSM Enable ???
With Regards

Sga_max_size

Hi,
I have a question about the parameter sga-max-size.
When starting the instance, oracle9i r2 on linux redhat, it seems that the total sga comes near to that sga-max-size parameter. As far as I understand is this used for dynamic sga, so you can increase db_cache_size etc on the fly. But does it also mean that the size of the SGA is already completely in the memory of the system? How can you see on Linux Redhat 9 how much memory Oracle is using, if it is really using the completely SGA (for example 1GB)?
thanks
greets

it seems that the total sga comes near to that sga-max-size parameter
r.- Explanation about this point: if the SGA components exceed the SGA_MAX_SIZE value the instance is not going to start.
As far as I understand is this used for dynamic sga, so you can increase db_cache_size etc on the fly
r.- It is true
But does it also mean that the size of the SGA is already completely in the memory of the system?
r.- Part of them. While the SGA is higher the memory in your machine is more used. But it does not mean that if you have 1GB in SGA it means that 1GB it is need of RAM. Really as far as I know Oracle software does not inform us in what proportion it uses the memory and so on. Oracle software and documentation learn us how the SGA must be handle.
How can you see on Linux Redhat 9 how much memory Oracle is using
r.- You have several ways to find out those values.
1.- command : "top"
2.- Create a script using "ps" command
Joel Pérez
http://otn.oracle.com/experts

Sga_max_size is it recommended ?

Good Morning to all ;
I need to check few things about ( oracle instance registration). So i am trying to create new DB.
My pfile parameters are db_name=proddb
compatible=10.2.0
instance_name=prodins
sga_max_size=900m
control_files ='/u01/app/oracle/oradata/proddb/control01.ctl'
background_dump_dest=/u01/app/oracle/admin/proddb/bdump
core_dump_dest=/u01/app/oracle/admin/proddb/cdump
user_dump_dest=/u01/app/oracle/admin/proddb/udump
undo_management=auto
undo_tablespace=undotbs
~
When i am executing catalog.sql script i am getting following error ;
create or replace public synonym DBA_AUDIT_STATEMENT for DBA_AUDIT_STATEMENT
ERROR at line 1:
ORA-04031: unable to allocate 3888 bytes of shared memory ("shared
pool","unknown object","sga heap(1,0)","kglsim object batch")
grant select on DBA_AUDIT_STATEMENT to select_catalog_role
ERROR at line 1:
ORA-04031: unable to allocate 3888 bytes of shared memory ("shared
pool","unknown object","sga heap(1,0)","kglsim object batch")
comment on table DBA_AUDIT_STATEMENT is
ERROR at line 1:
ORA-04031: unable to allocate 3888 bytes of shared memory ("shared
pool","unknown object","sga heap(1,0)","kglsim object batch")
from user_audit_trail
ERROR at line 10:
ORA-04031: unable to allocate 3888 bytes of shared memory ("shared
pool","unknown object","sga heap(1,0)","kglsim object batch")
comment on table USER_AUDIT_STATEMENT is
ERROR at line 1:
ORA-04031: unable to allocate 3888 bytes of shared memory ("shared
pool","unknown object","sga heap(1,0)","kglsim object batch")
create or replace public synonym USER_AUDIT_STATEMENT for USER_AUDIT_STATEMENT
ERROR at line 1:
ORA-04031: unable to allocate 3888 bytes of shared memory ("shared
pool","unknown object","sga heap(1,0)","kglsim object batch")
grant select on USER_AUDIT_STATEMENT to public
ERROR at line 1:
ORA-04031: unable to allocate 3888 bytes of shared memory ("shared
pool","unknown object","sga heap(1,0)","kglsim object batch")
from dba_audit_trail
ERROR at line 9:
ORA-04031: unable to allocate 3888 bytes of shared memory ("shared
pool","unknown object","sga heap(1,0)","kglsim object batch")
create or replace public synonym DBA_AUDIT_OBJECT for DBA_AUDIT_OBJECT
ERROR at line 1:
ORA-04031: unable to allocate 3888 bytes of shared memory ("shared
pool","unknown object","sga heap(1,0)","kglsim object batch")
grant select on DBA_AUDIT_OBJECT to select_catalog_role
ERROR at line 1:
ORA-04031: unable to allocate 3888 bytes of shared memory ("shared
pool","unknown object","sga heap(1,0)","kglsim object batch")
comment on table DBA_AUDIT_OBJECT is
ERROR at line 1:
ORA-04031: unable to allocate 3888 bytes of shared memory ("shared
pool","unknown object","sga heap(1,0)","kglsim object batch")
from user_audit_trail
ERROR at line 9:
ORA-04031: unable to allocate 3888 bytes of shared memory ("shared
pool","unknown object","sga heap(1,0)","kglsim object batch")
comment on table USER_AUDIT_OBJECT is
ERROR at line 1:
ORA-04031: unable to allocate 3888 bytes of shared memory ("shared
pool","unknown object","sga heap(1,0)","kglsim object batch")
create or replace public synonym USER_AUDIT_OBJECT for USER_AUDIT_OBJECT
ERROR at line 1:
ORA-04031: unable to allocate 3888 bytes of shared memory ("shared
pool","unknown object","sga heap(1,0)","kglsim object batch")
grant select on USER_AUDIT_OBJECT to public
ERROR at line 1:
ORA-04031: unable to allocate 3888 bytes of shared memory ("shared
pool","unknown object","sga heap(1,0)","kglsim object batch")
from dba_audit_trail
ERROR at line 13:
ORA-04031: unable to allocate 3888 bytes of shared memory ("shared
pool","unknown object","sga heap(1,0)","kglsim object batch")
create or replace public synonym DBA_AUDIT_EXISTS for DBA_AUDIT_EXISTS
ERROR at line 1:
ORA-04031: unable to allocate 3888 bytes of shared memory ("shared
pool","unknown object","sga heap(1,0)","kglsim object batch")
grant select on DBA_AUDIT_EXISTS to select_catalog_role
ERROR at line 1:
ORA-04031: unable to allocate 3888 bytes of shared memory ("shared
pool","unknown object","sga heap(1,0)","kglsim object batch")
comment on table DBA_AUDIT_EXISTS is
ERROR at line 1:
ORA-04031: unable to allocate 3888 bytes of shared memory ("shared
pool","unknown object","sga heap(1,0)","kglsim object batch")
select u.name, o.name from user$ u, obj$ o where 1=2
ERROR at line 2:
ORA-00604: error occurred at recursive SQL level 1
ORA-04031: unable to allocate 3888 bytes of shared memory ("shared
pool","unknown object","sga heap(1,0)","kglsim object batch")
CREATE OR REPLACE PACKAGE utl_raw IS
ERROR at line 1:
ORA-04031: unable to allocate 3888 bytes of shared memory ("shared
pool","unknown object","sga heap(1,0)","kglsim object batch")
ERROR:
ORA-04031: unable to allocate 3888 bytes of shared memory ("shared
pool","unknown object","sga heap(1,0)","kglsim object batch")
DOC>######################################################################
DOC>######################################################################
DOC> The following PL/SQL block will cause an ORA-20000 error and
DOC> terminate the current SQLPLUS session if the user is not SYS.
DOC> Disconnect and reconnect with AS SYSDBA.
DOC>######################################################################
DOC>######################################################################
DOC>#
DECLARE
ERROR at line 1:
ORA-04031: unable to allocate 3888 bytes of shared memory ("shared
pool","unknown object","sga heap(1,0)","kglsim object batch")
Disconnected from Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - Pr oduction
With the Partitioning, OLAP and Data Mining options
sga_max_size is it recommended to use in pfile ? ormust i change sga_target instead of sga_max_size ?
Thanks ..

*[oracle@linuxserver ~]$ ls -ltr $ORACLE_HOME/dbs/*
total 112
-rw-r----- 1 oracle oinstall 8385 Sep 11 1998 init.ora
-rw-r----- 1 oracle oinstall 12920 May 3 2001 initdw.ora
-rw-rw---- 1 oracle oinstall 1544 Mar 12 11:40 hc_orcltest.dat
-rw-rw---- 1 oracle oinstall 24 Mar 12 11:41 lkORCLTEST
-rw-rw---- 1 oracle oinstall 1544 Mar 12 11:54 hc_orclprod.dat
-rw-rw---- 1 oracle oinstall 24 Mar 12 11:55 lkORCLPROD
-rw-rw---- 1 oracle oinstall 1544 Mar 14 01:05 hc_asdf.dat
-rw-rw---- 1 oracle oinstall 1544 Mar 14 02:56 hc_testdb.dat
-rw-rw---- 1 oracle oinstall 24 Mar 14 02:58 lkTESTDB
-rw-r----- 1 oracle oinstall 1536 Mar 14 03:05 orapwtestdb
-rw-r----- 1 oracle oinstall 1536 Mar 14 03:44 orapworcltest
-rw-r----- 1 oracle oinstall 1536 Mar 14 04:05 orapworclprod
-rw-r--r-- 1 oracle oinstall 56 Mar 14 23:13 alert_orclprod.log
-rw-r--r-- 1 oracle oinstall 695 Mar 14 23:14 sqlnet.log
-rw-r----- 1 oracle oinstall 2560 Mar 14 23:14 spfiletestdb.ora
-rw-r----- 1 oracle oinstall 3584 Mar 14 23:47 spfileorclprod.ora
-rw-r----- 1 oracle oinstall 1536 Mar 15 00:49 orapwprod
-rw-rw---- 1 oracle oinstall 1544 Mar 15 00:50 hc_prod.dat
-rw-rw---- 1 oracle oinstall 24 Mar 15 01:07 lkPRODDB
-rw-r----- 1 oracle oinstall 1536 Mar 15 02:40 orapwsbiprod
-rw-rw---- 1 oracle oinstall 1544 Mar 15 02:44 hc_sbiprod.dat
-rw-rw---- 1 oracle oinstall 24 Mar 15 02:45 lkSBI
-rw-r----- 1 oracle oinstall 2560 Mar 15 10:39 spfileorcltest.ora

SGA_MAX_SIZE=high

Hi All,
os:HP unix
Db:oracle 10g
db size 20gb
load:normal
i have 32Gb of memeory...if i set sga_max_size=16g...any impact in future?
what will be the impact if i set sga_max_size set to high value....
can any one suggets me for the best values....
thanks,
dbc

dbc001 wrote:
Hi All,
os:HP unix
Db:oracle 10g
db size 20gb
load:normal
i have 32Gb of memeory...if i set sga_max_size=16g...any impact in future?
what will be the impact if i set sga_max_size set to high value....
can any one suggets me for the best values....
thanks,
dbc General thumb rule for setting the oracle memory againt RAM is oracle should get 60-70% of total memory. But this may differ in many conditions.
So first you need to check whats 'sga target advisory','db cache advisory','shared pool cache advisor' and pga advisor are saying about the cahce sizes? Take a report from AWR, so that you will get the idea if increasing SGA would help. Also you can check from v$sga_target_advice
Also read super post from below;
http://asktom.oracle.com/pls/asktom/f?p=100:11:0::::P11_QUESTION_ID:488583600346559562
Now coming to impact if SGA set to very high - well in that case your OS wont get enough memory for its processing and can bring down whole database performance. Then also there would be lots of swapping of pages from disk to memory and viceversa.Also there can be high CPU utilization because oracle has to keep large part of buffers in cahce and its processing will take cpu

Sga_target vs sga_max_size

Hi,
I'm using ASMM and sga_target is set to 1000M.
the sga_max_size parameter should be have the same value as sga_target?
For example: what's happen if i set sga_max_size to 1200M ?
Thank's

Hi,
I think, that if you set sga_max_size to 1200M and you have SGA_target=1000M, then you could dynamicaly (without restarting instance) increase sga up to 1200M. SGA_MAX_SIZE is only about possibility to increase your sga and oracle DOESN'T allocate whole SGA_MAX_SIZE - it allocate only your sga_target.
You can test it by decreasing SGA_TARGET by command ALTER SYSTEM SET SGA_TARGET=800M SCOPE=MEMORY; and you can see that memory will be released. You can test it in other direction too - increase sga_target to 1200M and aditional memory will be allocated from free memory.
Pavel

Sga_max_size vs sga_target

Whats the difference between SGA_MAX_SIZE and SGA_TARGET? I am bit confused.
As per Oracle® Database Reference 10g Release 1 (10.1)
SGA_MAX_SIZE specifies the maximum size of the SGA for the lifetime of the instance
Then why SGA_TARGET is used.
I am missing something here. Kindly clarify.
Thanks in Advance
SID.

Max_size is what the SGA can grow to if it has to.
SGA_Target is what you'd like the SGA to be.
Then why SGA_TARGET is used.
Because you might want to dynamically grow your SGA, above the target. Suppose someone gives you a transportable tablespace and it comes from a 4K-blocksize database, and you're using 8K blocks. You have to 'alter system set db_4k_cache_size=something', but if you try that when your TARGET already equals your MAX_SIZE, you'll be told there's no room to grow the SGA, so the only way to achieve what you want is to shrink some other part of the SGA or to set the parameter in your init.ora and bounce. Either could be problematic on a production box. That's just one example: remember that 'SGA_TARGET' is indeed only a target: Oracle is allowed to exceed the target if thinks the workload makes it necessary to do so.
So the difference between MAX_SIZE and TARGET is 'slack space': memory that's not in use, but could be if you (or Oracle) determined a need for it.
On a lot of operating systems, this difference is paged out and thus doesn't mean you're wasting real, physical memory.
But on others (and I think this is true of Windows and Linux), you would indeed be 'consuming' that memory difference -which would thus amount to wasted physical memory.

Sga_max_size & memory_max_target

Similar Messages

Maybe you are looking for