SGA & PGA Optimization

Hi to All,
Exist a method in order to optimize SGA & PGA, installing a DB in Oracle DB 10g?
Best Regards
Gaetano

Automatic Shared Memory Management(ASMM)
Requirements:
SGA_TARGET >0
STATISTICS_LEVEL=TYPICAL or ALL.
The below mentioned parameters are auto-tuned by oracle.
SHARED POOL
LARGE POOL
JAVA POOL
DB CACHE
Refer to Note:295626.1 from Metalink.(SGA)
Refer to Note:223730.1 from metalink (PGA)

Similar Messages

Oracle 11g SGA & PGA setup

Hi I installed oracle 11g & create database , now i want to use fully optimize database.
Currently my DB server RAM is 16GB, how should i allocate SGA for this.If i used oracle 11g automatic memeory management feature to allocate SGA+PGA, how should i use them.Currentlymy SGA is set to 4GB, Please advise

Hi,
It is depends upon the workload which you have in your organization(future and present situation)
SGA+PGA size will be automatically managed by Oracle. No need to worry about this.
If you need to increase Memory_Max_Size, you can also increase the Memory size in the future.
Thanks

SGA/PGA (Memory) in RAC environment.

Guys,
I would like to get your inputs on SGA / PGA settings on a RAC database.. Does LMS/LMON/LMD process use memory which is part of PGA or these process allocate memory at OS level ?
I would like to see the usage of Memory used by a database.
below sql from Mr. Kyte's website i have used. Somehow i am not getting real usage of the system. Any help would be appreciated.
Thanks
select
ssst.sid,
stn.name ,
round(ssst.value/1024/1024,2) memory ,
USERNAME,
COMMAND,
OSUSER,
MACHINE,
TERMINAL,
PROGRAM ,
ssst.STATISTIC#
from v$statname stn,v$sesstat ssst , v$session ses
where stn.STATISTIC# = ssst.STATISTIC# and
ssst.sid = ses.sid and
name like 'session%pga%memory%'
order by 3 asc ;
Edited by: P explorer on Aug 28, 2009 9:56 PM

From sql script, that get "session pga memory","session pga memory max" each of session in oracle database(on that node)
You'll see
sid: session id
memory:
if "session pga memory" = pga memory in this session now
if "session pga memory max"= maximum pga memory in this session.
program: os program name
More deatails abour v$session http://download.oracle.com/docs/cd/B19306_01/server.102/b14237/dynviews_2088.htm#REFRN30223
If need to know all PGA size in that node
"session pga memory":
select
round(sum(ssst.value)/1024/1024,2) memory
from v$statname stn,v$sesstat ssst , v$session ses
where stn.STATISTIC# = ssst.STATISTIC# and
ssst.sid = ses.sid and
name ='session pga memory';
"session pga memory max":
select
round(sum(ssst.value)/1024/1024,2) memory
from v$statname stn,v$sesstat ssst , v$session ses
where stn.STATISTIC# = ssst.STATISTIC# and
ssst.sid = ses.sid and
name ='session pga memory max';
Or if you need to check PGA memory all nodes (RAC)
COLUMN username FORMAT A20
COLUMN module FORMAT A20
SELECT a.inst_id,
NVL(a.username,'(oracle)') AS username,
a.module,
a.program,
Trunc(b.value/1024) AS memory_kb
FROM gv$session a,
gv$sesstat b,
gv$statname c
WHERE a.sid = b.sid
AND a.inst_id = b.inst_id
AND b.statistic# = c.statistic#
AND b.inst_id = c.inst_id
AND c.name = 'session pga memory'
AND a.program IS NOT NULL
ORDER BY b.value DESC;

SGA & PGA target

Hi all,
My questions is regarding how to set up SGA & PGA target values giving DB server is MS 2003 Enterprise 64 edition sever with 63 GB of RAM. Our DB’s version is 10.2.0.3 and RACed with 2 instances.
Currently our setting for SGA is 23 GB and PGA is 4 GB. I ran the memory advisor it display different optimal values for those two instances (35 GB and 23 GB for SGA, 5 GB and 4 GB for PGA). Guess our db is not well balance loaded.
I would like to know if there is any rule(s) that SGA can’t be more than certain percentage of total RAM for the server.
Thanks a lot in advance.
Have a great weekend!!
Shirley

Hi
Here is my approach:
1) consider free physical memory (meassure must be taken with Oracle down)
2) substract a 10% of that amount as a margin
3) if the box is exclusive for Oracle, the remaining amount may be your SGA+PGA limit
4) if not is exclusive, then substract memory required for other services, then you'll get the SGA+PGA limit.
5) Substract your PGA size, giving the SGA figure
For instance
59 Gb - 6 Gb = 53 Gb - 4 Gb = 49 Gb
(63 Gb -4 Gb [estimated OS footprint + IO cache]) = 59 Gb free physical memory
Setting PGA+SGA beyond the free physical memory figure, may lead to swaping and degraded system performance.
Regards
http://oracledisect.blogspot.com

SGA, PGA and... little extra?

Will oracle process use some extra "non oracle" memory for OS related stuff?
Mean, not considering SGA, I connect a database process and I see:
SQL> select p.program,
2 p.spid, pm.category, pm.allocated/1024 allocated, pm.used/1024 used, pm.max_allocated/1024 max_allocated
3 from V$PROCESS p, V$PROCESS_MEMORY pm
4 where p.pid = pm.pid
5 and p.spid =2650;
                                                                                                        Max
                                                                          Allocated       Usedd   allocated
PROGRAM                        SPID                     CATEGORY                 Kb          Kb          Kb
oracle@uxlabhost11             2650                     SQL                      14           9          42
oracle@uxlabhost11             2650                     PL/SQL                   56          34          57
oracle@uxlabhost11             2650                     Other                  1501                    1501That's allocated PGA after having connected and done nothing else
So it somehow allocated 1.4 Mb upon start-up...
Now question is. Do oracle processes use OS memory which cannot be considered as SGA or PGA?
Reason being my trying to estimate memory needs for a database server. Many I've read correct formula should be SGA + max allocated PGA + some_extra_just_in_case...
Is there an estimate on how much that "some_extra_just_in_case" would be per process?
If OS dependent, I'm implementing on RHEL 6...
thanks

So, I've used pmap...
Got 257 enties in the form "4096K rw-s- /dev/shm/"
since we are using AMM , that should do for PGA and SGA ... some 1052672 Kb, which process is attached to...
yet pmap then continues to display other entries....
0000002a95557000      4K r-x-- /opt/oracle/product/11g/lib/libodm11.so
0000002a95558000   1024K ----- /opt/oracle/product/11g/lib/libodm11.so
0000002a95658000      4K rw--- /opt/oracle/product/11g/lib/libodm11.so
0000002a95659000      4K rw---    [ anon ]
0000002a9565a000    392K r-x-- /opt/oracle/product/11g/lib/libcell11.so
0000002a956bc000   1024K ----- /opt/oracle/product/11g/lib/libcell11.so
0000002a957bc000     40K rw--- /opt/oracle/product/11g/lib/libcell11.so
0000002a957c6000      4K rw---    [ anon ]
0000002a957c7000    864K r-x-- /opt/oracle/product/11g/lib/libskgxp11.so
.. TRUNCATED...
0000003fb810a000     64K rw---    [ anon ]
0000003fbbd00000     84K r-x-- /lib64/libnsl-2.3.4.so
0000003fbbd15000   1020K ----- /lib64/libnsl-2.3.4.so
0000003fbbe14000      4K r---- /lib64/libnsl-2.3.4.so
0000003fbbe15000      4K rw--- /lib64/libnsl-2.3.4.so
0000003fbbe16000      8K rw---    [ anon ]
0000007fbffde000    136K rwx--    [ stack ]
ffffffffff600000      4K r-x--    [ anon ]
total          1276452KNotice "total 1276452K"
So you saying non SGA/PGA would be 1276452 - 1052672?
That would be too much... yet if pmap another process, almost all flags (hex column) but [ stack ] are the same....
So how to tell which of those are shared and which are "exclusive" to the process, i.e: The "some extra just in case" mem...
thanks

SGA+PGA Size allocation

Hi all
I Have a server System Configuration with
RAM size: 16GB Ram & Hard disk Size of 1TB.
I Installed Oracle 11g R2 in the server System
I want to Allocate Dedicated Memory for oracle..
How Should i calculate the Memory size of SGA+PGA for good Performance..

Pl do not post duplicates - Reg:-SGA & PGA Memory Allocation Size

Reg:-SGA & PGA Memory Allocation Size

Hi all
I Have a server System Configuration with
RAM size: 16GB Ram & Hard disk Size of 1TB.
I Installed Oracle 11g R2 in the server System
I want to Allocate Dedicated Memory for oracle..
How Should i calculate the Memory size of SGA+PGA for good Performance..

Check MOS
*How to calculate the memory used by dedicated and shared servers? [ID 551415.1]*

SGA/PGA Sizes ???

I need help!
I have a Windows 2003 Server (w/sp2) with 4GB of RAM & 2 CPUs. Oracle 10.2.0.2 is installed.
ASMM is ENABLED by default (and it still is)
These are my sga/pga settings:
pga_aggregate_target = 1G
sga_max_size = 1504M
sga_target = 1000M
shared_pool_size = 504M
sort_area_size = 262144000 (250M)
large_pool_size = 104M
db_cache_size = 104M
I believe I should DISABLED ASMM, correct? Otherwise, my settings aren't used.
Based on my 4GB, I think Oracle can use 2GB of that.
What should I set the settings above too?
...thanks

First if you use Oracle's automatic memory management feature and provide spfile parameter values for parameters that are automatically managed by Oracle then the provided values are taken as minimum values for these areas. There are other situations where values for parameters like sort_area_size which is limited to 5% of pga_aggregate_target are in fact still referenced.
With a pga_aggregate_target of 1G I do not see any valid reason why you would have a sort_area_size set to 250M. What is the reason for this?
What kind of environment is this: OLTP, DSS, OLAP?
How many concurrent sessions?
Dedicated vs shared server?
Why do you not want to use automatic memory management? What problem have you encountered?
HTH -- Mark D Powell --

Sga&pga

Hi all;
i wanna learn something about sga and pga... I have r11 instance on linux and db version is 10.2.0.3...Let say my sga=5 Gb and pga is=3gb...my server has 20gb ram...when i look my usage by top command and i see that:
Mem: 20550320k total, 20491732k used why linux allocate all those area?
i have 20 Gb ram and sga+pga=8 soo which oracle process use 12 Gb?
and advicer gives me adivice about SGA... it offers 10 Gb SGA... if i rise my sga what is my benefit? what it would change?
thanks alot

Hi hussien;
Thanks for again answers and help
You need to identify what other processes are running on this node. For example, if you have CM running on the database tier node, then it is expected to find more memory allocated. You can simply stop all the services on the server and start it one by one, and each time and keep an eye on the allocated memory.Its my mistake, coz i talked wiht my client and they said me they are working on this machine and thatswhy i had this memory usage.. sory for this mistake again (but your post helped me alot,coz i asked them what they are doing for a now ,and they gave me that answer :),thanks for leading)
Since you are on 10g, I would suggest you also go through the following document.
Note: 295626.1 - How To Use Automatic Shared Memory Management (ASMM) In Oracle10g
https://metalink2.oracle.com/metalink/plsql/ml2_documents.showDocument?p_database_id=NOT&p_id=295626.1
If you still have any queries, please feel free to post it here.Thanks for note.. i am reading it and its soo usefull for me, thanks for sharing your knowledge here wiht us hussein..
you are an oracle angle :)
regards
Helios
Edited by: helios on 12.May.2009 06:58

SGA, PGA and SHMMAX Setting

If I have set SHMMAX to 8GB (on 64bit linux) value, does that mean that my SGA+PGA values need to remain within 8GB limit? If my SGA size is 6GB and PGA size is 4GB, does that mean that my OS is going to allocate two shared memory segments?

The SHMMAX parameter is used to define the maximum size (in bytes) for a shared memory segment and should be set large enough for the largest SGA size.
http://www.idevelopment.info/data/Oracle/DBA_tips/Linux/LINUX_8.shtml
http://books.google.co.in/books?id=2ImPFP6Yk64C&pg=PA357&lpg=PA357&dq=PGA+is+included+in+SHMMAX&source=bl&ots=On3S7-CEX0&sig=LhOYOO946hrPZh-cIUEzWNiwpRg&hl=en&ei=xyLOTJqaC4yYvAONm7T3Dw&sa=X&oi=book_result&ct=result&resnum=5&ved=0CCwQ6AEwBA#v=onepage&q&f=false
Please close the thread as answered.

Analysis sga/pga growth

Hi,
We using oracle version 11.2.0.1 on AIX 6 and we using OEM.
I am asked to gather last one week stats (high level and lower level in a day)for tablespace,SGA,PGA and resource_limit ,open_cursor parameter.
How to collect it.Is there any query to find it ?
Thanks,

922884 wrote:
Hi,
Thanks for your repsonse.
Architect asking that.
Can i use DBA_HIST_SGA ,DBA_HIST_SGAstat for sga and DBA_HIST_TBSPC_SPACE_USAGE ,DBA_HIST_TABLESPACE_STAT for tablespace.
could you tell for resource_limit and open_cursor.How to collect those values ?
ThanksWhen you start with the wrong question, no matter how good an answer you get, it won't matter very much.
Do you realize that OPEN_CURSOR is a per session limit?

SGA/PGA best practice

With an XE limitation of 1GB for the PGA and SGA, how would one best preserve this limitation?
In other words, how would one minimise the PGA and SGA usage via ones interface with Oracle?
For instance, in a SQL query I was building I could either (The query has multiple aggregates on multiple tables in a 'one to many' join relationship):
1) Use WITH clauses
2) Use inline views
3) Use standard views
4) Use temporary tables
5) Maybe more possibilities
Without much of an insite into how Oracle 'works' it's difficult to gauge which of these is less 'resource hungry'.
Possibly there is a reference on how to use the PGA & SGA efficiently?
Or possibly a more definitive explanation on what's actually stored in these memory areas (rather than just 'prorgam' and 'system' data).
Regards all,

SGA is used in 2 main areas: parsing the SQL and avoiding disk reads by having stuff in memory. There is one SGA for all of XE instance.
PGA is used heavily for sorting, hash joining and 'working stuff'. The PGA is created for each Dedicated Server process. Much of the PGA is inside the SGA for Shared Server processes
SGA: (There are exceptions to each of these 'Rules Of Thumb' or 'ROT' statements)
Good coding technique will allow reuse of SQL and avoid as much as possible reparsing;
Use bind variables;
Do not create SQL on the fly;
Avoid dynamic SQL (concat strings to create SQL on the fly);
Forget about tweakiing the buffer cache as it is mainly a performance thing that you can't do much about in XE;
WITH clause is nice as it may reduce the count of subqueries;
Leave it with 'automatic memory management' (again a perf hit, but it will attempt to optimize mem availability);
Don't reinvent - Use the features that are loaded as they will likely get statements out faster, releasing memory faster;
Stored Views may (often do) grab unneeded table data. When joining to stored views, see whether they can be replaced by cleaner code;
Do not create SQL on the fly.
PGA:
Use shared server when feasible (at risk of performance hit);
Global Temp Tables go into PGA, watch the use;
Maximize reuabale SQL, minimze all other languages (remote or in DB) including PL/SQL;
Watch for PGA wasters such as UNION vs the better UNION ALL, and unneeded sorts;
PGA is 'swapped out' to Temporary tablespace. Make sure temp tablespace big enough ... it's not counted in the 4GB disk;
Avoid using COMMIT except at end of transaction. Avoid COMMIT in loops. Make sure undo tablespace is big enough ... it's not counted in the 4GB disk ;
Did I mention it's not a good idea to create SQL on the fly?

Oracle Concepts: Query on SQL Processing (execution in SGA/PGA)

Hi,
I need some clarity on my understanding, suppose there is a query:
SELECT t1.c1, t1.c2
FROM t1, t2
WHERE t1.c3 = t2.c1
ORDER BY t1.c1;User A submits above query and following steps are executed:
Syntax Check -in PGA
Semantic Check -in PGA
Shared Pool Check (unsuccessful) -in SGA
Optimization (Hard Parse) -in SGA
Row Source Generation (Hard Parse) -in SGA
Execution - in SGA?User B submits same query and following steps are executed:
Syntax Check -in PGA
Semantic Check -in PGA
Shared Pool Check (successful) -in SGA
(Soft Parse)
Execution - in SGA?First question (General):
I thought Execution happens in SGA, but sorting, hashing, and/or merging bitmaps happens in PGA (temporary segment) so is it a sub-part of Execution that happens in user's PGA?
Second question (For user B):
Once Shared Pool Check is successful, and plan/data-sets are already in SGA, so sorting, hashing, and/or merging bitmaps will happen on these data-sets in user B's PGA again?
Regards,
Ankit Rathi
http://oraclenbeyond.blogspot.in

OnB wrote:
Hi,
I need some clarity on my understanding, suppose there is a query:
SELECT t1.c1, t1.c2
FROM t1, t2
WHERE t1.c3 = t2.c1
ORDER BY t1.c1;User A submits above query and following steps are executed:
Syntax Check -in PGA
Semantic Check -in PGA
Shared Pool Check (unsuccessful) -in SGA
Optimization (Hard Parse) -in SGA
Row Source Generation (Hard Parse) -in SGA
Execution - in SGA?User B submits same query and following steps are executed:
Syntax Check -in PGA
Semantic Check -in PGA
Shared Pool Check (successful) -in SGA
(Soft Parse)
Execution - in SGA?First question (General):
I thought Execution happens in SGA, but sorting, hashing, and/or merging bitmaps happens in PGA (temporary segment) so is it a sub-part of Execution that happens in user's PGA?The execution happens in the SGA(Buffer cache) but any kinds of such processing like sorting is session specific and that's why it happens in the PGA of that user.
>
Second question (For user B):
Once Shared Pool Check is successful, and plan/data-sets are already in SGA, so sorting, hashing, and/or merging bitmaps will happen on these data-sets in user B's PGA again?Yes.
That said, can you post a link that confirms that the syntax/semantics check happen in the PGA? AFAIK it's not really a part of the PGA because oracle's code itself would store the grammar and would do it .
Aman....

AWR SGA+ PGA usage

Hi
We're doing some performance testing on our database. The SGA is set to 1.5GB and PGA set to 0.5GB. At some point we are runnning out of memory as we ramp up the number of users and transactions .
What I'm looking for is to graph the PGA and SGA usage seperately regular intervals (a line graph) showing their increaase as users ramp up.
Anyone any ideas on how I can get this information whether through AWR or manually.
Thanks in advance.

You have not posted the version you are on. You should use automatic pga management and unset the values for areasize parameters (if there is no specific reason for keeping them).
ORA-04030: out of process memory when trying to allocate 8389132 bytes (pga heap,redo read buffer)
Doing block recovery for file 3 block 76812
Resuming block recovery (PMON) for file 3 block 76812What are the OS level statistics of memory usage ?
It simply means that Oracle (rather OS...as Oracle is also going to request memory from OS only) is running out of memory. Most common reason behind that is use of features like bulk collect without any limit clause which causes the pga memory to grow beyond pga_aggregate_target...and finally sucking all the memory available. Further requests for memory allocation start failing with ORA-04030.
Also, please post the output from v$pgastat using tags.
Edited by: amardeep.sidhu on Nov 24, 2010 9:29 AM

SGA, PGA & RAM Size?

our DB running in dedicated server mode(FYI).
am defining my SGA size 500MB, which is half the size of DB server 1gb RAM, it does not mean that my instance will not go beyond 500mb, if multiple users are connected & start using Sorts,(SORT_AREA_SIZE =1mb), apart from 500mb, each user whoever using sort area space will be allocated 1mb space in 1gB RAM, is it correct?
since SORT_AREA_SIZE can be modified at session level,each user can set their own sort area size, which may lead to paging, is it correct?
Sorts uses memory from PGA,PGA is not part of SGA,hence how to determine the PGA size?, is there any init.ora parameter for sizing PGA in ORACLE 8.1.7?

The size of PGA will depends upon the containts of PGA which are Sort Area, Session Statistics Information, Stack Space, Cursor Information
I am not aware of any parameter to size the PGA.
I will check the documentation and will let you know.
Manu

SGA & PGA Optimization

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