Sga confusion

Hi,
I am running oracle 10.2.0.4 on RHELAS U4.6 and kernel is Linux 2.6.9-67.ELhugemem #1 SMP i686 i686 i386 GNU/Linux.
Current RAM of the system is 32GB and current sga size is 3G.
My question over here is that is it possible that I can increase the sga_target=4G and sga_max_size=8G?
One thing more my installed OS is 32-bit
Thank you for your cooperation.
Kind Regards,
Adnan Hamdus Salam.
Edited by: adnan on Feb 15, 2012 2:28 AM
Edited by: adnan on Feb 15, 2012 2:29 AM

Hi,
So I have to perform these steps.
But in my case I already set the shmmax to 4G and
none 16G 0 16G 0% /dev/shm
other values are
oracle soft memlock 1048576
oracle hard memlock 1048576
what will be the rest of steps?
Did not understand this as given below:
The following parameter should be added to the spfile or pfile.
use_indirect_data_buffers=true
Also, any references to db_cache_size and db_xK_cache_size parameters should be removed and replaced with the old style db_block_buffers parameter entry.
# 3Gig for an 8K db_block_size. ((3 * 1024 * 1024) / 8) = 393216
db_block_buffers = 393216
Thank you for your help and support.
Kind Regards,
Adnan Hamdus Salam

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Confusion on how oracle works in SGA

i did the following
Session 1
conn user/password
exec num(2000);/* this procedure generates numbers and inserts in a table on the xxx tablespace */
Plsql procedure completed
CommitCommit complete
Session 2 /// this session is run simultaneously with session 1 using another terminal.
conn sys/<password> as sysdba
alter tablespace xxx offline normal
tablespace altered>
The problem is when the procedure is running I tried to turn the tablespace offline ..
But the tablespace gets offline and the procedure is still running . and also I have commited the trasaction when the tablespace is offline. The commit is successful. The commit should be unsuccessful bcos the tablespace is offline.
i am using oracle 10g R2 version on windows vista.
can anyone also give me any links or info on how oracle actually works when i give a DML query. like insert. or update..

but the procedure was still running when the
tablespace went offline normal.
How sure are you that the procedure was still successfully modifying the data ? It should have generated Oracle error ORA-00376: file N cannot be read at this time the moment the tablespace went off line.
Is the code short enough to post ? (If so, don't forget the "code" tags - see FAQ at top right - to get a fixed font display).
Is it not that dirty buffers are still being written
and the tablespace has gone offline!The session updating the data should fail as the tablespace status is changed, and the database writer will be triggered to write all the dirty blocks from that tablespace to file before the tablespace offline is completed.
>
Do you mean to say that there are still dirty buffers
belonging to the tablespace even after a checkpoint
and the tablespace being down!No.
Regards
Jonathan Lewis
http://jonathanlewis.wordpress.com
http://www.jlcomp.demon.co.uk
P.S. Here's a cut-n-paste from a SQL*Plus session running 10.2.0.1 as the tablespace holding table t1 - with one row in it - is taken offline a few moments after the pl/sql starts running:
SQL> insert into t1 values(1);
1 row created.
SQL> commit;
Commit complete.
SQL> get afiedt.buf
1 begin
2 for i in 1..1000000 loop
3 update t1 set n1 = ln(i);
4 end loop;
5* end;
SQL> /
begin
ERROR at line 1:
ORA-00376: file 6 cannot be read at this time
ORA-01110: data file 6: 'C:\ORACLE\ORADATA\DXR2\TEST_8K.DBF'
ORA-06512: at line 3

SGA & PGA concept

We have a production Oracle 11g DB in which SGA_TARGET is 0 but ASSM is enabled but the documentation on Oracle says that if SGA_TARGET is 0 means that ASSM is disabled. Also, PGA_AGGREGATE_TARGET is 0 but Maximum PGA allocated is around 1 GB.
I hope, my question is clear that concept seems to be confusing where SGA_TARGET is 0 but ASSM is enabled and also PGA_AGGREGATE_TARGET is 0 but maximum PGA allocated is 1 GB.
Please revert with the reply to my query.
Regards

972145 wrote:
Thanks for your reply but there is some confusion. ASMM is automatic shared memory management which seems to be similar to AMM which is automatic memory management. ASMM can be seen from OEM under Database Configuration->Memory Advisors. I guess, there is ASM which is automatic storage management to do with reduntant copies of data to provide fault tolerance.
ASMM - 10g setting for the automatic SGA using the parameter sga_target .
AMM - 11g setting for both SGA and PGA, uses the parameter memory_target
ASM - Automatic Storage Management, nothing to do with SGA or PGA
ASSM - Automatic Segment Space Management, for the tables and nothing to do with the PGA and SGA
Aman....
Edited by: Aman.... on Jan 21, 2013 3:53 PM corrected the typo

Max SGA size in 32bit OS

Hi,
I have a EBS Production Instance (12.1.1) in a 32-bit OS (RHEL4.0).
RAM: 16GB, SWAP: 8GB
Our sga size is 1.7GB
Is there any way to increase our SGA size.
Please advice.
Thanks in advance.

You can use BIG PAGES
For more info you can read the below docs:
http://www.oracle-base.com/articles/linux/LargeSGAOnLinux.php
32-bit Architecture and the hugemem Kernel
The RHEL 3/4 smp kernel can be used on systems with up to 16 GB of RAM. The hugemem kernel is required in order to use all the memory on systems that have more than 16GB of RAM up to 64GB. However, I recommend the hugemem kernel even on systems that have 8GB of RAM or more due to the potential issue of "low memory" starvation (see next section) that can happen on database systems with 8 GB of RAM. The stability you get with the hugemem kernel on larger systems outperforms the performance overhead of address space switching.
With x86 architecture the first 16MB-896MB of physical memory is known as "low memory" (ZONE_NORMAL) which is permanently mapped into kernel space. Many kernel resources must live in the low memory zone. In fact, many kernel operations can only take place in this zone. This means that the low memory area is the most performance critical zone. For example, if you run many resources intensive applications/programs and/or use large physical memory, then "low memory" can become low since more kernel structures must be allocated in this area. Low memory starvation happens when LowFree in /proc/meminfo becomes very low accompanied by a sudden spike in paging activity. To free up memory in the low memory zone, the kernel bounces buffers aggressively between low memory and high memory which becomes noticeable as paging (don't confuse it with paging to the swap partition). If the kernel is unable to free up enough memory in the low memory zone, then the kernel can hang the system.
Paging activity can be monitored using the vmstat command or using the sar command (option '-B') which comes with the sysstat RPM. Since Linux tries to utilize the whole low memory zone, a low LowFree in /proc/meminfo does not necessarily mean that the system is out of low memory. However, when the system shows increased paging activity when LowFree gets below 50MB, then the hugemem kernel should be installed. The stability you gain from using the hugemem kernel makes up for any performance impact resulting from the 4GB-4GB kernel/user memory split in this kernel (a classic 32-bit x86 system splits the available 4 GB address space into 3 GB virtual memory space for user processes and a 1 GB space for the kernel). To see some allocations in the low memory zone, refer to /proc/meminfo and slabtop(1) for more information. Note that Huge Pages would free up memory in the low memory zone since the system has less bookkeeping to do for that part of virtual memory, see Large Memory Optimization (Big Pages, Huge Pages).
If you install the RHEL 3/4 hugemem kernel ensure that any proprietary drivers you are using (e.g. proprietary multipath drivers) are certified with the hugemem kernel.
In RHEL 2.1, the smp kernel is capable of handling up to 4GB of RAM. The kernel-enterprise kernel should be used for systems with more than 4GB of RAM up to 16GB.
Above article taken from http://www.puschitz.com/TuningLinuxForOracle.shtml#32BitArchitectureEdited by: user00726 on Aug 6, 2010 2:02 AM

Confusion over ASM

Hi All,
i was going through ASM docs and so far my understanding " its is purely an instance which has got only the metadata of all the RDBMS instances using that ASM"
In ASM instance we dont have redo log file, datafiles etc then what is the functionality of DBWr and LGWr background processes in ASM instnace?
Regards,
ASM

Hans Forbrich wrote:
Aman,
Even I started with the misinterpretation that ASM handles I/O for the database. Not quite correct.
In the simplest explanation of ASM I've come up with is: Actual database I/O is 'raw', with the benefit that ASM manages the table of contents of the disk. The database server process asks ASM where to start reading; the DBWR asks ASM where to start writing - both server process and DBWR still operate.
"The Oracle ASM instance manages the metadata and provides space allocation for the Oracle ASM files. When a database instance creates or opens an Oracle ASM file, it communicates those requests to the Oracle ASM instance. In response, the Oracle ASM instance provides file extent map information to the database instance."
This is taken from the 11gR2 ASM manual in Chapter 1 http://download.oracle.com/docs/cd/E11882_01/server.112/e10500/toc.htm at Fig 1-1
Hans,
Thanks so much for the correction and for the link. I stand corrected, ASM does teh metadata writes only, the actual data IO operations are handled by the db's background processes only.
Just now, I opened [ASM Under the Hood book|http://www.amazon.com/Oracle-Automatic-Storage-Management-Under/dp/0071496076] and was reading it to find the answer and page no 44 clearly mentioned the same what you have just said. Here is a note from the same page about DBWR ,
>
This processes manages the SGA buffer cache in the ASM instance. DBWR writes out dirty buffers ( changed metadata buffers ) from ASM buffer cache to disk. >
Which I believe is a very clear explanation that ASM processes just maintain metadata stuff. Thanks so much once again!
@Gurfan, Eduardo,
Apologies for any confusion that I unknowingly have created. Please read Hans's reply and mine over here.
regards
Aman....
Edited by: Aman.... on Oct 10, 2009 7:24 AM corrected page no, it was 44 :-( .

Allocating memory to SGA

Dear Friends,
I'm in little bit confusing of allocating memory to SGA area. My server has 1024MB memory. can u tell me what are the percentage should i allocate each segment ( shared Pool, buffer cashe , Large Pool , Java Pool , PGA target )
It is grate help to me.
Regards
upul Indika.

Oracle Performance Tuning Guide has following note, same strategy can apply to other pool like shared_pool
.2.2 Sizing the Buffer Cache
When configuring a new instance, it is impossible to know the correct size for the buffer cache. Typically, a database administrator makes a first estimate for the cache size, then runs a representative workload on the instance and examines the relevant statistics to see whether the cache is under or over configured.
http://download-west.oracle.com/docs/cd/B19306_01/server.102/b14211/memory.htm#sthref485
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I was reading RAC documents that is written by Steve Karam.
Cache Fusion for RAC
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http://www.dba-oracle.com/t_implementation_decision_rac_clusters.htm
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Rakesh Soni.

I'm confused whether each instance has it's own redo log file or they are centrally stored. The above document says that each instance has it's own redo log files.No it is not...
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PGA vs SGA

hi,
i read the documents which says that pga has individual user datas like bind variables.session info.
here oracle how the pga communicate with sga for execution.
what are the components for PGA
thanks
with regards

user3266490 wrote:
hi,
i totally confused about PGA and shared pool.is there any relation between librarcy cache and pga.
whether,when the user exeutes select,insert,update,delete these are in librarcy cache or PGA.
i read that parsing,optimzation,execution,fetching there are happening in Library cahe.
so why oracle created the runtime area in PGASo why there is a confusion? The parsing, execution, they are all happening in the SGA because what is needed is that if someone else also requires the same data, for example, the same execution plan, the same data buffers, it should all be accessible from the SGA which is going to be shared among the users. But the PGA contains the data structures which don't do this! Answer this, when you do an order by , does it mean that all the other users also start seeing teh data in the order by clause by default? The answer should be no. This sorted data is just kept in the pga of yours. Similarly, there is a bind variable which is shared among the users but two different users need to use two different values of it.Where it is best to keep those different values, in their own PGAs isn't it? Hence its the private memory of the sessions.
HTH
Aman....

Several processes write to the SGA during database operation.

Greeting to all ;
From following official document says Memory Architecture
Several processes write to the SGA during database operation.
I thinks DBWn writes updated information from dbbc to data files.
   Server process is fetching required information from data files.
Several processes write to the SGA during database operation !
- What are they ?

8f953842-815b-4d8c-833d-f2a3dd51e602 wrote:
Thanks sybrand_b
Several processes write to the SGA during database operation.
So your answer is client process for DML opearations. Ok , i got it.
From the same link , Memory Architecture
The server and background processes do NOT reside within the SGA, but exist in a separate memory space.
        Partially i can understand above statement. Here i have little confusion also - please clarify.
SGA + background process = INSTANCE.
Server process is only available when user is intracting with database.
From official document , bgprocess , server process exist in a separate memory space -
- if so , what is name of the memory area ?
    Thanks in advance ..
Which memory area? The one holding the SGA? The one holding the executing code for any one of the background processes? The one holding the code for any of the several server processes?
Go here: Oracle Database Instance
and take a look at figure 13-1 and its surrounding discussion.

Solaris hangs when Oracle SGA is too large

I am an Oracle DBA with preconfigured Solaris servers. Our Unix admin is outsourced so we don't have a lot of good support here. When I set the instance SGA too large the server hangs and requires a hard reboot It seems that the error is due to insufficient memory or swap. Is this normal behaviour for Solaris 10? Shouldn't the process abend before the server does?

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Steve324 wrote:
s there a solution to get things
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See my previous suggestions

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