Performance Tuning :: Optimal REDO Log File Size
Feb 10, 2011
I would like to make a change on the live system!I have read a book and found a information about REDO log file size is impact on DB performance.My DB current log file size is 100 MB. But, Oracle 10g's Redo Logfile Sizing Advisor offer the optimal log file size is 1845 MB.What REDO log file size is best for my Oracle database?
#Optimal log file size:
select optimal_logfile_size
from v$instance_recovery
----------------------------
OPTIMAL_LOGFILE_SIZE
1842
[code]....
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Apr 6, 2011
The REDO log file size is important DB performance issues when DB is run archivelog mode.If DB run noarchivelog mode, REDO log file size not impact to DB performance.
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Jun 18, 2012
In one of our envirnoment i could see the redo size is high.Trying to understand why this is more
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Feb 25, 2011
I try to current redo log file location to multiplex redo log configuration. I did do this on the DB.I import a backup file to DB when I made this change, but its too slow running import process from old configuration. Approximately it is 4 times slow.
when I recovery old configuration for redo log file, import process is normal running...Why this changes hit to DB import process performance? The old redo log file location is below:
GROUP#MEMBERBYTES
4"/crtest1/oradata/redo04a.log"524288000
4"/crtest1/oradata/redo04b.log"524288000
3"/crtest1/oradata/redo03a.log"524288000
3"/crtest1/oradata/redo03b.log"524288000
2"/crtest1/oradata/redo02a.log"524288000
2"/crtest1/oradata/redo02b.log"524288000
1"/crtest1/oradata/redo01a.log"524288000
1"/crtest1/oradata/redo01b.log"524288000
The new multiplex redo log file location is below:
GROUP#MEMBERBYTES
4"/crtest1/oradata/redo04a.log"524288000
4"/opt/redolog/redo04b.log"524288000
3"/opt/redolog/redo03a.log"524288000
3"/usr/redolog/redo03b.log"524288000
2"/usr/redolog/redo02a.log"524288000
2"/disk1/redolog/redo02b.log"524288000
1"/disk1/redolog/redo01a.log"524288000
1"/crtest1/oradata/redo01b.log"524288000
I think that new configuration is better for old configuration at security issue.Here is the disk partitions on the server:
-bash-3.00$ df -lh
Filesystem size used avail capacity Mounted on
/dev/dsk/c0t0d0s0 9.6G 2.2G 7.3G 23% /
/devices 0K 0K 0K 0% /devices
ctfs 0K 0K 0K 0% /system/contract
[code]....
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Aug 31, 2012
I have a standalone DB of version 10.2.04.I am facing log file parallel write as one of the top events.I have increased the REDO log file size to 500m.But even then REDO switching is happening frequently.
select group#, bytes, archived, status, first_change#, first_time from v$log order BY first_change#;
GROUP# BYTES ARC STATUS FIRST_CHANGE# FIRST_TIME
---------- ---------- --- ---------------- ------------- ----------
10 262144000 NO INACTIVE 8509999 30-08-2012
12 524288000 NO INACTIVE 8612142 30-08-2012
11 262144000 NO INACTIVE 8676390 30-08-2012
9 262144000 NO CURRENT 8706330 30-08-2012
[code]....
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Mar 17, 2006
How can I disable redo generation for DML statements.
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Mar 24, 2013
how do you limit oracle redo?
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Jul 1, 2010
How to Find Out Which SQL Statements Causing excessive Redo generation?
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Aug 13, 2010
This morning when I checked my archive logs, I suprised that the redo files are generating after every 3 min and each of file size is 50M, which is the actual size of both log members. I m using RAC database with DR server.Usally the total redo logs quantity for one day is 4 to 5. but since 10 pm of yesterday to 7 am today, the quantity of log files are 109, each of 50 M .
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Aug 10, 2011
I am running Oracle 10.2.0.1.0 on MS Windows 2003 server 64-bit with 16G RAM.
Here is the findings for my Oracle database.
SQL> select * * from v$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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May 9, 2011
Objective : To find solution to archieve data from 2 big tables which is occupying maximum size in the data base. With current data (From Jan 2005 to Sept 2011) it has records as mentioned below:
transaction - 41687927
trnansaction_dtl - 83945934
We need to load data and run monthly batches from October 2011 to current month which will increase this space.
1. Issue is there will not be having so much space.
2. Maintenance of such table is diffcult now.Also there is huge impact on performance. Can we think of partitioning the table base on date aswe query 1st table based on certain date range?
3. Most of reports use this table and creating performances issues
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Feb 14, 2013
We have a table emp_details with 23772889 records. Our requirement is to increase few of the columns size in the table emp_details. We are following the below alter statement which is taking around 2 hours of time.
ALTER TABLE emp_details
MODIFY
(
address char(90)
,department char(30)
)
/
Is there any way to improve the above query performance?
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Apr 22, 2013
I have got the following error yesterday
ORA-01555 caused by SQL statement below (SQL ID: fdxcyoin67ty8t, Query Duration=380128 sec, SCN: 0x0229.ff00afd0):
following are the existing settings
SQL> show parameter undo
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
undo_management string AUTO
undo_retention integer 96000
undo_tablespace string undo
[code]....
following are the details from v$undostat
select begin_time, end_time, undotsn, undoblks, maxquerylen, maxqueryid, activeblks, unexpiredblks, expiredblks, tuned_undoretention from v$undostat
where trunc(begin_time)=trunc(sysdate)-1 order by begin_time;
BEGIN_TIME END_TIME UNDOTSN UNDOBLKS MAXQUERYLEN MAXQUERYID ACTIVEBLKS UNEXPIREDBLKS EXPIREDBLKS TUNED_UNDORETENTION
-------------- -------------- ---------- ---------- ----------- ------------- ---------- ------------- ----------- -------------------
21-04-13 00:08 21-04-13 00:18 1 12733 378446 duqnawh32hp4u 91152 7068448 225440 345600
21-04-13 00:18 21-04-13 00:28 1 8951 379047 duqnawh32hp4u 99344 7072800 225440 345600
21-04-13 00:28 21-04-13 00:38 1 14073 379650 duqnawh32hp4u 90128 7075872 234656 345600
[code]....
Following are the details in AWR report (00:00 til 01:00 of 21-Apr-2013) .... not thet the error was produced at 00:42
Undo Segment Summary DB/Inst: DBCPY/dbcpy01 Snaps: 18853-18854
-> Min/Max TR (mins) - Min and Max Tuned Retention (minutes)
-> STO - Snapshot Too Old count, OOS - Out of Space count
-> Undo segment block stats:
-> uS - unexpired Stolen, your - unexpired Released, uU - unexpired reUsed
[code]....
Undo Advisor information taken 'now' is as following
SQL> select dbms_undo_adv.longest_query(sysdate-2,sysdate) from dual;
DBMS_UNDO_ADV.LONGEST_QUERY(SYSDATE-2,SYSDATE)
----------------------------------------------
379650
SQL> select dbms_undo_adv.required_retention from dual;
[code]....
In above situation what should be my first choice (assuming increasing space is not an issue) - increase undo tablespace or increase undo retention?
If latter is the choice then what should be the value? Because as I understand present 96000 value is taken as lower limit and because of auto tuning the actual value (TUNED_UNDORETENTION) being used was 345600 In that case shall I set it to something > max(maxquerylen) i.e 379,650 + X?Or I shall increase the undo tablespace size?
From Undo Advisor output it looks to me that even if I increase the undo retention to 379650 current undo size will be able to support it (may be at the expense of DMLs)Is that right?
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Nov 25, 2011
All the analysis till now on our system proves that our system is clearly I/O bound and db sequential read is the biggest culprit.
We have even identified the index which is being affected by sequential read. I am thinking of creating a new tablespace with 32K blocksize (currently all table spaces are 8k) and migrate this index to the new space. That way, Oracle will have to do less number of reads to get the required data.
But is there anything wrong in having just one tablespace with a differnt block size? Or is there anything that I have to be watchful about while doing it?
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Aug 9, 2012
Which is the correct method to calculate actual data size in a table? becaue when I serach in google, I saw the below line.
"Oracle thumb rule says (actual space required for a table + 30 % space) will calculate the original space requirement for a table."
Method 1:
actual space = num_rows*avg_row_len
Method 2:
actual space = (Num of rows in a table) * (Avg_row_len) + ((Num of rows in a table) * (Avg_row_len)* 0.3)
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Aug 11, 2011
I need to take the database trace of each page of my web application. I am giving the following commands.
BEGIN
dbms_monitor.session_trace_enable(session_id=>122, serial_num=>NULL, waits=>true, binds=>true);
END;
Accessing the web application. Once it renders completely, I am executing the following command.
BEGIN
dbms_monitor.session_trace_disable(session_id=>122);
END;
In the user_dump_dest folder, I am expecting to see a new trace whenever I execute these commands. But the same trace file is getting updated. How do I make oracle to create a new trace for each iteration. I am using Oracle 11g Release on CentOS 5.x
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May 28, 2013
is it Any way I can put the size of my redo log (During Install Oracle DB 11.1.0.7 )
I mean during installtion .??? becouse its by default 50 MB I need to be 200MB
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Apr 10, 2013
i want to know about trace file and TKPROF. any example.
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Oct 15, 2013
I am getting back into Oracle (from a long haul in MS only env.) and am now testing Oracle installs.I have been given a task of seeing the diff. between 12c and 10.2g...I set up 2 vms (excatly same configs) and used the same dmp file (on both env.) to restore data and settings for our jobs to run.We have some aggregated data, and cubes with DIM tables each being run on the vm machines. We run nightly jobs to rebuild our cubes.
I am supposed to see/analyze the value of 12c, and understand things might vary from company to company, but am perplexed at my result.12c is half the speed of 10.2g, both env. are the same out of the box with same dmp file and same hardware.
I am using the same dmp file, with the same jobs on each machine, with both vms having 10.2g or 12c installed out of the box as is.what default oracle settings might have changed from 10.2g to 12c that could make the exact same env. run twice as slow on the 12c?
Expectations were that out of the box with both machines running same jobs on same data (from dmp files) would have it that 10.2g would be slower than the 12c, except the 12c takes 2 times as long to run the jobs. I have reviewed every possibility as I know usually the problem is the person sitting in the chair and not the pc...but I confirmed all was identical from the one vm env. to the other, except the version of oracle out of the box.
What could be done to bring that default setting back to atleast equal time between the 2, that would give me a great starting point. Otherwise, I would have to toss this up to bloatware.
I read up a bit on the CBO, and know this might have changed in 12c.is there a way to bring it back to a backwards ealier config, so as to atleast match both env. execution plans?
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Jan 13, 2011
find the attached tkprof'ed file of session
I started the trace after the query started (upon user's complaint)
However even after tracing the session for more than 30 minutes I am not geeting where the 30 minutes are accounted in this file
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Nov 16, 2011
I executed a query which executed quickly (1.7 seconds) but since its output took time in displaying on the console the time shown by 'set timing on was 39.5 seconds
also I took trace (tkprof) for the same.My query is why the timings under 'Total Waited' (43.19 and 1.69) are not added to the elapsed time 1.83 seconds
call count cpu elapsed disk query current rows
------- ------ -------- ---------- ---------- ---------- ---------- ----------
Parse 1 0.00 0.00 0 0 0 0
Execute 1 0.00 0.06 0 10 0 0
Fetch 758 0.03 1.77 0 0 0 11345
------- ------ -------- ---------- ---------- ---------- ---------- ----------
total 760 0.03 1.83 0 10 0 11345
[code]....
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Apr 13, 2011
In a 3-node RAC setup; one node is showing high CPU utilization around 40~50%. The CPU utilization was less than 20% 10 days back but from 9th oldest day it jumped and consistently shows the double figure. I ran AWR reports on all three nodes and found one node with high CPU utilization and shows below tops events-
EVENT WAITS TIME(S) AVG WAIT(MS) %TOTAL CALL TIME WAIT CLASS
CPU
time 5,802 34.9
RFS
ping 15 5,118 33,671 30.8 Other
Log file sequential
read 234,831 5,036 21 30.3 System I/O
Sql*Net
more data from
client 24,1711,08745 6.5 Network
Db file sequential
read130,939 4533 2.7 User I/O
Findings:-
On AWR report(file attached) for node= sipd207; we can see that "RFS PING" wait event takes 30% of the waits and "log file sequential read" wait event takes 30% of the waits that occurs in database.
1)Are these symptoms of undersized log buffer?
2)I feel Network wait can be reduced by tweaking SDU & TDU values based on MDU.
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Apr 21, 2011
I ran a scp command to transfer a file from local server to a remote server. when I am trying to kill the process, its giving an error.
ksh: kill: 19258: No such process
If I do a ps -ef | grep scp its showing the process running, but if i try to kill it, its showing me error.
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Jun 8, 2012
We have one primary oracle database 10.2 and standby by database with no data guard. Initially we have 2 redo log group in primary and standby database.
We have recently add 2 more redo log and increase the size of log member from 50m to 200m in primary database. We don't have any problem in primary database.but in standby database we face a problem because we cannot open it. It always in mount stage in which . How we change the size of current redo log because we can't run. Alter system switch logfile command in mount stage.
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Apr 13, 2011
I am using oracle 8.1.5 database and my temp01.dbf file size is increased upto 19.8 GB now i want reduce its size .
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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 1, 2011
what exactly redo log file contains.? whether they contained the ddl or dml statements or more than that.........?
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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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Aug 20, 2010
redo generation. As I found the below statement in another forum."Undo segment generates the redo data also, because undo segment is database changes, so it generates the redo data also."
How a Undo segment can generate Redo and Undo datas.
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