Performance Tuning :: How To Configure SGA_MAX_SIZE Parameter
Sep 24, 2013
The Memory tuning advisor has recommended that I increase the size of the SGA_TARGET to 5G, from my current size of 3G.
SQL> select * from v$sga_target_advice order by sga_size;
SGA_SIZE SGA_SIZE_FACTOR ESTD_DB_TIME ESTD_DB_TIME_FACTOR ESTD_PHYSICAL_READS
---------- --------------- ------------ ------------------- -------------------
1536 .5 1555141 1.667 7251211
2304 .75 949130 1.0174 4572127
3072 1 932898 1 2258733
3840 1.25 930939 .9979 2168835
4608 1.5 929819 .9967 2005529
5376 1.75 929166 .996 2005529
6144 2 928980 .9958 2005529
7 rows selected.However, the SGA_MAX_SIZE parameter is set to 3G, so when I do:
SQL> ALTER SYSTEM SET sga_target=5376M scope=both;
ALTER SYSTEM SET sga_target=5376M scope=both
*
ERROR at line 1:
ORA-02097: parameter cannot be modified because specified value is invalid
ORA-00823: Specified value of sga_target greater than sga_max_size
My database used spfile. I know that the procedure to change this is the following: Create pfile from spfile, shutdown immediate, change value in pfile, startup with pfile..However, the pfile does not have any parameter called max_sga_size. It only has the following:
<dbsid>.__sga_target=3221225472
*.sga_target=3221225472
how to change sga_max_size?
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May 24, 2013
To tune the OID11g the DB parameter recommendation is :
sga_target Minimum 60% of RAM
sga_max_size Minimum 60% of RAM
db_cache_size Minimum 60% of RAM
So what is RAM size..is that the RAM size on the linux BOX which is 8 GB in my case
or RAM size assigned to Oracle DB?
If I take RAM size 8 GB I am not able to modify the parameter. I am getting below error:
SQL> alter system set sga_max_size=4916M scope=both;
alter system set sga_max_size=4916M scope=both
*
ERROR at line 1:
ORA-02095: specified initialization parameter cannot be modified
how to check that total memory assigned to Oracle DB?
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Nov 27, 2011
we are ruining oracle 9i in windows 2000 server, oracle is the only database running in the server. The RAM capacity is 4GB but the sga showing is as below
Total System Global Area 118255568 bytes
Fixed Size 282576 bytes
Variable Size 83886080 bytes
Database Buffers 33554432 bytes
Redo Buffers 532480 bytes
pga size
NAME VALUE
---------------------------------------------------------------- ----------
aggregate PGA auto target 0
global memory bound 0
total expected memory 0
total PGA inuse 19937280
[code]...
how can we using the 4gb RAM deducing 20% for OS Sometimes users are complaining slow process.
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May 16, 2013
How to set commit_write parameter to 'BATCH' in another session.
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Mar 2, 2011
In my below query example , i have to pass more than 4000-5000 paramter in "a1.num" in below query. what is the best way to handle this, also if I pass more than 2000 paramter , the query takes a long time to execute. How can we solve the performance issue as well how I can pass more parameter.
SELECT c1, c2,
TO_CHAR (c3, 'HH24:MI'),
c4,
c5,
[code]...
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Jul 12, 2010
Looking to understand the difference between instance tuning and database tuning.
What is the difference between these two tuning exercises? I understand that an instance is memory based structures (logical) where as database consists of physical structures.
However, how does one tune a database the physical structure? Does it have to do with file placements/block sizes etc. Would you agree that a lot of that is taken care by ASM now in 11g? What tools are required/available (third party as well as oracle supplied) for these types of tuning scenarios?
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Oct 31, 2011
I have two tables with 113M records in DWH_BILL_DET & 103M in prd_rerate_chg_que and Im running following merge query, which is running for 13 hrs to update records, which is quiet longer time.
SQL> explain plan for MERGE /*+ parallel (rq, 16) */
INTO DWH_BILL_DET rq
USING (SELECT rated_que_rowid,
detail_rerate_flag_code,
rerate_sel_key,
[code].....
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Sep 30, 2010
How the length of column width effects index performance?
For example if i had IOT table emp_iot with columns:
(id number,
job varchar2(20),
time date,
plan number)
Table key consist of(id, job, time)
Column JOB has fixed list of distinct values ('ANALYST', 'NIGHT_WORKED', etc...).
What performance increase i could expect if in column "job" i would store not names but concrete numbers identifying job names.
For e.g. i would store "1" instead 'ANALYST' and "2" instead 'NIGHT_WORKED'.
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Jun 16, 2010
I have a question about database fragmentation.I know that fragmentation can reduce performance in query times. The blocks are distributed in many extents and scans process takes a long time. Oracle engine have to locate the address of the next extent..
I want to know if there is any system view in which you can check if your table or index has high fragmentation. If it's needed I will have to re-create, move or rebulid the table or index, but before I want to know if the degree of fragmentation is high.
Any useful script or query to do this, any interesting oracle system view?
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Oct 20, 2010
There is a simple way to increase the performance of a query by reducing the row-size of the table it hits. I used it in the past by dividing the table into smaller parts and querying respective smaller table in each query.
what is this method called ? just forgot the method and can't recall it. what this type of row-reduction optimization is called ?
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Jun 16, 2011
How many records could I have in a single table without performance degradation with Standard Edition without partitioning with cutting-edge server (8 or 12 cores, 72 GB RAM, FC 4 Gbit, etc...) and good storage?
300 Millions in only one table with 500K transactions / day is too much?
Simple database with simple schema.
How many records begin to be too many?
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Nov 15, 2010
Testing our 9i to 11g upgrade, we've imported the entire DB into the new machine.We've found that certain procedures are really suffering performance problems. BUT, we've also found, that if we check out a production copy of the procedure from our source code control, and reinstall it, the performance issue goes away. Just alter the procedure and recompiling does NOT work.
The new machine where the 11g database exists is slightly different than the source, but it's not like we have this problem with every procedure. It's only a couple.
any possible reason that we'd have to re-install a procedure to correct a performance problem?
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Apr 12, 2013
I need to check the package performance and need to improve the package performance.
1. how to check the package performance(each and every statement in the package)?
2. In the package using the delete statement to delete all records and observed that delete is taking long time to delete all the records in the table(Table records 7000000). This table is like staging table.Daily need to clean the data before inserting the data into it. what can I use instead of Delete.
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Aug 9, 2010
Somewhere I read that we should not use hints in Oracle production environments, but we can use hints in the development environment and on achieving the desired execution plan we can adjust the 'statistics' to follow that plan without hints.
Q1. If it is true what statistics do we adjust for influencing the execution plan and how?
For example, I have the following simple query:
select e.empid, e.ename, d.dname
from emp e, dept d
where e.deptno=d.deptno;
emp.empid, emp.deptno and dep.deptno columns have indexes and the tables have the standard structure as found in the basic oracle examples.
If I look at the execution plan of the above query then I see that the driving table is empand the driven table is dept.Also the type of join that is taking place is 'Nested Loop'.
Questions: With respect to the above query,
Q 2. If I want to make dept the driving table and emp the driven table then how can I adjust the statistics to achieve that?
Q 3. If I want to use hash join instead of a nested loop join then then how can I adjust the statistics to achieve that?
I can put the ordered and the use_hash hint to effect this but again I have heard that altering statistics is a more robust way to control an execution plan as compared to hints.
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Dec 6, 2011
I have an issue with export(expdp).
When i exporting an user using expdp utility, the load the on the server is going up-to 5. The size of the database is 180GB. Below is the command that i use for export.
expdp sys/xxxx directory=dbpdump dumpfile=expdp_trk_backup.dmp logfile=expdp_trk_backup.log exclude=statistics schemas=trk
Do i need any look into any memory parameters for this?
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May 28, 2013
I am having 11gr2 database on a 2 node RAC cluster . OS is RHEL version 5.8When i change the SGA_MAX_SIZE to 5GB, after i bounce it shows as 15GB.
I am trying to set my SGA_TARGET and SGA_MAX_SIZE to 5G. But after bouncing SGA_MAX_SIZE is showing as 15GB and not as 5GB
I also tried edit in pfile and then create spfile and started up with spfile. But still same i am observing.
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Oct 17, 2011
The following query gets input parameter from the Front End application, which User queries to get Reports.There are many drop down boxes like LOB, FAMILY, BRAND etc., The user may or may not select values from drop down boxes.
If the user select any one or more values ( against each drop down box) it has to fetch all matching values from DB. If the user does'nt select any values it has to fetch all the records, in this case application will send a value 'DEFAULT' (which is not a value in DB ) so that the DB will fetch all the records.
For getting this I wrote a query like below using DECODE, which colleague suggested that will hamper performance.From the below query all the variables V_ are defined in procedure which gets the values selected by user as a comma separated string here V_SELLOB and LOB_DESC is column in DB.
DECODE (V_SELLOB, 'DEFAULT', V_SELLOB, LOB_DESC) IN
OPEN v_refcursor FOR
SELECT /*+ FULL(a) PARALLEL(a, 5) */
*
FROM items a
WHERE a.sku_status = 'A'
[code]...
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Sep 3, 2010
what the principal things to look at when we have for the same query different performance results are?I have 2 different bases: the plan and data are the same but performance results are very differents.
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Sep 21, 2010
I've done lots of reading about these two parameters, SGA_MAX_SIZE and DB_CACHE_SIZE.
What I understand now is, that setting db_cache_size to a target value and setting all other buffer cache setting to 0 will enable Oracle 9i to automatically manage buffer cache values, right? This is, per meta link document 223299.1 the most important parameter in Oracle 9i regarding memory management.
Now, SGA_MAX_SIZE set the maximum value at wich I can increase the db_cache_size to?
The question is ; WHY? Why should I allocate 1G of RAM to my oracle instance and not set the db_cache_size to the exact same value? What happens with the difference in memory between the SGA_MAX_SIZE and the DB_CACHE_SIZE, ex :
SGA_MAX_SIZE = 1000M
DB_CACHE_SIZE = 500M
What happens with the 500M left over, is it used for anything ?
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Jun 28, 2012
I was just wondering how is the relationship between MEMORY_TARGET and SGA_MAX_SIZE parameters, if exists any at all.I set my memory parameters as:
# Enable AMM
MEMORY_MAX_SIZE=10G
MEMORY_TARGET=4G
# Disable ASMM
SGA_TARGET=0
SGA_MAX_SIZE=0
So I bounce my instances and when I checked the parameter SGA_MAX_SIZE, Oracle automatically set a value of 2456M to it:
sga_max_size big integer 2456M
sga_target big integer 0
Reading MOS ID 443746.1, there is no clear mention about this relationship. It seems that Oracle automatically set SGA_MAX_SIZE as 60% of MEMORY_TARGET.
In am running Oracle 11gR2 (11.2.0.2.3) under Red Hat Linux.
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Mar 17, 2012
are the most important performance keys we have to calculate or take in account to preserve or to increase the DB performance in terms of response times, and whatsoever according to performance ?
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Jul 4, 2013
I would like to know if using varchar parameter in sql queries with number column can result in performance degrade.
Ex: Procedure testa ( myparam varchar) is
begin
select col1 into var1 from table where colno = myparam;
end;
Here col no is a number column and myparam is varchar. I feel its better to change the parameter to number.
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Mar 27, 2013
I am working on an assignement where client is using Oracle 10g but stuck to using RBO Now the application team, from the GUI available to them build dynamic queries and some of them run very slow.
Neither the code can not be changed to tune the queries nor do we get the exact step in the plan which is an issue (being RBO).For some long running queries the Tuning advisor is not producing any recommendations.
Another hurdle is that all the application users are using same application user id so we can not write a logon trigger to use CBO for some particular queries to see what is happening in the background!
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Jul 4, 2012
I want to tuning the next sql sentence. In this sql I want to get the hash_value and sql_text of the sentences that it's causing TX blocks. Is it possible?. This sentence works fine but sometimes It's slow.
SELECT DISTINCT hash_value,
sql_text
FROM gv$sql sq
WHERE hash_value IN (SELECT DISTINCT prev_hash_value
FROM gv$session se
WHERE sid IN (SELECT sid
FROM gv$lock l
WHERE type = 'TX'
AND ctime >= 2000
AND l.inst_id = se.inst_id
AND l.sid = se.sid)
AND sq.inst_id = se.inst_id);
[code]....
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Nov 2, 2012
I see one of my SQL's which is ran by the user on a 10.2.0.3 database changing its SQL_ID after some runs even if the query is not changed a bit! However the HASH VALUE for this query remains the same.
how a same query can have different SQL_ID's but same HASH_VALUE?
Note: Statistics are not modified on the base tables of this query.
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Aug 10, 2011
I am running Oracle 10.2.0.1.0 on MS Windows 2003 server 64-bit with 16G RAM.
Here is the findings for my Oracle database.
SQL> select * * from v$sgainfo;
NAME BYTES RES
-------------------------------- ---------- ---
Fixed SGA Size 1293560 No
Redo Buffers 7094272 No
Buffer Cache Size 830472192 Yes
[code]...
I find that the SGA component "Buffer Cache" is decreasing from the start "1.8G" and down to now 0.8G. On the other hand, the component "Shared Pool" is increasing from the start 0.3G to now 1.2G. I noticed that there are 100 operations of shrinking of "Buffer cache" and growth of "Shared Pool" in Oracle every day.Is it a indicator that I should raise up the SGA_MAX_SIZE?
I tried to increase the SGA_MAX_SIZE to 4G. But I cannot start the Oracle afterward.Is it a limitation of MS Windows(OS) or Oracle?I set the SGA_MAX_SIZE to 3G. This time, I can startup Oracle.What is the optimum/maximum I can set to SGA_MAX_SIZE?Is there any adverse effect/concern when setting the SGA_MAX_SIZE more than 2G?
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Jul 11, 2012
Here i have three tier application. I want to know it host name from sid or sqlid . I want to know which query run on which host. Because i have one user from application to database. So i want to know which query consume more time on which host ?
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Mar 17, 2006
How can I disable redo generation for DML statements.
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Jul 26, 2011
I am getting enq: TS - contention as top event in AWR Report.where can i look into database to fix this issue.
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Aug 14, 2010
I want to run some OLTP benchmarks on my system. I have looked up the TPC-E benchmarking suite .. but the documentation on the site makes no sense to me .
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