Performance Tuning :: Required In Analyzing Network Waits From AWR
May 29, 2013
We are experiencing Network waits on one of our 2-node clustered databases...In every 1 hour of clock time we are finding 700-900 seconds of Network waits
From the AWR data I find that "ARCH wait on SENDREQ" is one of the main constituent for these Network waits and as such I suspect Network between Production database and its corresponding database might be slow
Question 1) Does this understanding look correct?
Question 2) Apart from the above what could be the other causes of the Network waits. Can we point out any particular area from following AWR extract...Seeing some gc* waits initially I thought it might be due to slow interconnect between the cluster nodes but some google search denotes it is not the case...So what could be other causes? I mean which network link I would check?
Snap Id Snap Time Sessions Curs/Sess
--------- ------------------- -------- ---------
Begin Snap: 22631 22-May-13 10:00:11 976 7.9
End Snap: 22632 22-May-13 11:00:28 978 8.1
Elapsed: 60.29 (mins)
DB Time: 795.66 (mins)
[code].....
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Mar 5, 2013
How can check database performance in a non-sequential parts of a day using AWR tool. For example, suppose we divide a day to 2 parts: low-traffic time and high-traffic time with the following time interval:
low-traffic time : 7:00am - 10:00am and 7:00pm - 11:00pm
high-traffic time : 10:00am - 01:00pm and 4:00pm - 06:00pm
I want to examine performance using snapshots gathered by AWR. If I get 2 AWR reports for low-traffic time of day (one for 7:00am - 10:00am, another for 7:00pm - 11:00pm ) and compute average of values in 2 reports, could I called it database performance in low-traffic part of day or not?
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Sep 26, 2012
what analyzing a table does to existing indexes? Do I need to rebuild the indexes after dbms_stats.gather_table_stats command ?
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Oct 3, 2010
Is there any relationship b/w tuning BUFFER CACHE and BUFFER BUSY WAITS?
1) Buffer Busy Waits are happening as the User process found the same Datablock is being used by another user in the BUFFER CACHE.
2) And also happens, when the server process found the same Datablock are being used in the Datafile.
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Apr 7, 2011
Following query is hanging either with 'Sequential access read' or 'Latch Free' wait event Important thing is the table which is self joined in subquery here does not have any index at all While it was hanged I tried to get trace of it and terminated twice. As such haven't got 'row source generataion' The table has only 120000 records and it shall update 34000 records
UPDATE invoice_header inv
SET inv.modified_due_date =
(SELECT inv1.btn_due_date
FROM invoice_header inv1
WHERE inv.dct_code = inv1.dct_code AND inv1.release = 'A5')
[code]...
During 'sequential read' using p1,p2 values tried to get what the session is reading and found that it is using the table itself.
During lath free I found following
SELECT name, 'Child '||child#, gets, misses, sleeps
FROM v$latch_children
WHERE addr= (select p1raw from v$session_wait where sid=18)
UNION
[code]...
However instead of self join when I creaed global temporary table as
create global temporary table t as select * from invoice_header where release='A5'
And used it in the update as
UPDATE invoice_header inv
SET inv.modified_due_date =
(SELECT t.btn_due_date
FROM t
WHERE inv.dct_code = t.dct_code AND t.release = 'A5')
WHERE inv.release = 'A5' AND inv.btn_due_date >= TRUNC (SYSDATE)
It updated the records in a second!!
Questions are
1) why it is producing 'sequential read' wait event when there is no index access or else why it is doing single block access when FTS is required?
2) Why is the 'latch free' wait event here and what it indicates here with 'cache buffer handles'?
Is it because we are reading and updating the same segment?
know in case DDL of table is required. It has all nullable columns and no index at all. Since it is 9i I am unable to use MERGE effectively in this case
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Nov 28, 2012
Recent events at work are forcing me to take a much closer look at hash joins in an attempt to understand them much deeper than just on the surface. But my question today is maybe simple. I have done lots of reading and can't for the life of me figure out how to get more memory to my HASH JOINS.
is there are way to get around this limit of 2GB on a box that has 64GB with some 20gb not in use?
1) my databases are all using workarea_size_policy=AUTO
2) I am not afraid to go back to =MANUAL and set my own work area sizes.
3) It seems I cannot set HASH_AREA_SIZE to more that about 2GB.
BANNER
--------------------------------------------------------------------------------
Oracle Database 11g Enterprise Edition Release 11.2.0.2.0 - 64bit Production
PL/SQL Release 11.2.0.2.0 - Production
CORE 11.2.0.2.0 Production
TNS for Solaris: Version 11.2.0.2.0 - Production
NLSRTL Version 11.2.0.2.0 - Production
18:40:31 SQL> alter session set hash_area_size = 6000000000 ;
alter session set hash_area_size = 6000000000
*
ERROR at line 1:
ORA-02017: integer value required
I know there is a limit of about 2GB on my box for HASH_AREA_SIZE and setting it to 2GB works fine. But it is still not enough.
18:50:22 SQL> alter session set hash_area_size = 2147483647;
Session altered.
Elapsed: 00:00:00.23
is there are way to get around this limit of 2GB on a box that has 64GB with some 20gb not in use? Using hash_area_size and 2GB, I get better performance than with my current PGA_AGGREGATE_TARGET doing the allocation for me.
I think I'd like to get as much as 20GB to specific sessions for hash joins but maybe I am pipe dreaming?
NAME TYPE VALUE
------------------------------------ ----------- -------------------
_pga_max_size big integer 1258280K
pga_aggregate_target big integer 6G
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Sep 22, 2011
I am getting the below error in alert log file,when my application calling a procedure.
ORA-01555 caused by SQL statement below (Query Duration=1576 sec, SCN: 0x09a2.5dda3165):
Fri Sep 16 16:33:40 2011
UPDATE SSPT_NETWORK_DETAILS SET INCLUDE_OFFERS = 'Yes' WHERE SESS_ID = SESS_ID
There is no ROLLBACK statement in my procedure. As per my understanding, the ORA-1555 error will occur,
1. The required old image is not in the undo,when we rollback the trasaction.
2. the select query may face this error because of delayed block cleanout concept.
But I don't know why this update statement causing this 1555 error?
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Jun 29, 2011
I ran an AWR report. The database looks fine, but a data load that loaded 1 Million rows an hour is now doing 500K per hour.
Wait Class Waits %Time -outs Total Wait Time (s) Avg wait (ms) %DB time
DB CPU 224 80.70
Other 2,668 0 28 10 9.99
System I/O 4,753 0 9 2 3.23
Administrative 1 0 6 5543 2.00
Commit 357 0 4 11 1.46
[code]....
The network value for wait: 630,601. What does this mean? Anything I should look at? When it was 1million per hour, the value was 4,563,000.
Top 5 Timed Foreground Events
Event Waits Time(s) Avg wait (ms) % DB time Wait Class
DB CPU 224 80.70
unspecified wait event 2,666 28 10 9.99 Other
control file sequential read 4,753 9 2 3.23 System I/O
switch logfile command 1 6 5543 2.00 Administrative
log file sync 357 4 11 1.46 Commit
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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).
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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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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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Oct 26, 2012
I have created materialized view which hold few million records.Should i have to analyze the view and compute the statistics after i create the materialized view?
Also, just in case i need further indexing, should i have to take the statistics for the table again?
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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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Sep 6, 2010
A question regarding analyzing behavior of partition table on Oracle -
Is analyzing different sub partitions within a partition is same as analyzing that partition and what about vice-versa?
Attached File(s)
untitled.JPG ( 9.2K )
Number of downloads: 3
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Jul 1, 2011
I have set of few hundred reports in Oracle Reports 6i and we have to distinguish them in 3 classes as simple, medium and complex reports. I was wondering what are all the various criterias that should be evaluated to do this .. for example the query behind the report or the layout or graphs complexity etc.
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Oct 25, 2013
I am using, Release 11.2.0.3.0 of oracle. In our database we observe, high 'Application' wait followed by 'other' and 'User I/O'. After investigating through the wait class 'Other', i found that 90% of the wait is due to wait event 'Enq: WF Contention ' that to excatly 5 PM to 5.30 PM daily. Then i found from the dba_hist_active_sess_history, that the sessions experiencing this waits are oracle internal(M004),
Now i can see two of the oracle jobs has been scheduled at this particular time.
1)dbms_autotask_prvt.age
2)dbms_scheduler.auto_purge
And these were having frequency daily.So, i am suspecting these were experiencing the waits. Now my question is, can i decrease the frequency(may be weekly) of these jobs and it will not put any negative impact on my DB? Or should change the schedule time to some less peak hour or whether these are 'not required' and can be disabled?
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Jul 1, 2010
We had a massive jump in cluster waits specifically; gc buffer busy acquire during an RMAN backup. We identified the cause of the waits to a few hot blocks with a table that may well need re-building in terms of ITLs and PCTFREE (Although I thorght ASSM would manage PCTFREE and PCTUSED..)
What happens during an RMAN backup that may cause huge cluster waits on hot tables? Is there some crazy redo issue going on or maybe flashback?
Either way the spike is there and we can pinpoint the activity on the database but just dont understand why RMAN would cause the issue.We have just found that the LARGE_POOL has not been set, in fact there is no SGA_TARGET either! Could this have an effect on RMAN and cluster waits?
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Oct 8, 2013
in the awr report I saw some segments in Segments by ITL Waits section. Number of waits reaches to 100 in 8-hour snapshot. Is it small/big number? Should I consider increase INITRANS or there is nothing to be worried because value 80-100 are not too high?
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Mar 22, 2013
os version is solaris 10
db version 11.2.0.3
how to tune log file sysnc waits in 11gr2 what parameters are involving in tuning log file sync and what would be its optimal values.
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Nov 23, 2010
We have a table (call it PROBLEM table) that varies between 60 and 100 million records from one data archival process to the next.The table has data from all 50 states and is range partitioned by each states unique code and has a primary key based on the following:
STATE the data is from
BMRK YEAR the year the data was last benchmarked
AREA location the data is from
SERIES industry the data is located in
YEAR the data was reported
MONTH the data was reported
DATA TYPE the type of data that was reported
ESTIMATE TYPE the type of statistical estimate that was produced from the data
REPORT ID report id unique to each state
REPT SFC state the reporter resided in
We have developed a job that will process data from other tables and create some statistics resulting in approx 2.2 million inserts, .5 million updates and .5 million deletes on PROBLEM table during each job run. Once this table is loaded another process (call this PROBLEM_PROCESS)takes off that reads this updated information to produce some statistical data that is stored in another table. This data is produced by summing anywhere between 2 and 5000 records per query from the PROBLEM table.Here is the query (call it PROBLEM_QUERY)
select round(sum(cm_value*sample_weight),3),round(sum(pm_value*sample_weight),3)
from matched_sample
where state_fips_code = :1
and area_fips_code = :2
and series_type_code = 'B'
and year = :3
and month = :4
[code]...
When we run this job it is very fast (20 minutes) until it gets to the PROBLEM_QUERY, at this point we get DB file scattered read waits, DB file sequential read waits and async IO waits and the job has run for as long as 2 days. When I look at grid, the PROBLEM query is doing a full table scan and ignoring the index.
Our systems people advised us to re-organize and re-index that data in the PROBLEM table after all of the DML and before the PROBLEM_PROCESS takes off. If we do this, it works and cuts our time down alot. However, the re-organize and re-index process adds eight hours to this process. Note: When we re-roganized the data we create a copy table on another set of table spaces and insert the data into the copy sorting the data on the primary key columns. After this we re-index the new table and drop the old table renaming the new table. When we do this later, we move the data back to another set of table spaces. So, we move the data back and for between table spaces A and B we can say.
We have Oracle installed on a M5000 server with Solaris as the OS the binaries and data files are stored on a NetApp Storage array(model 3160) of 500 1TB SATA 7200 RPM drives. However, there are 128 other databases on the NetApp filer as well.
IMO the array and the slow disks are the problem. I believe this because we are catering to the slow disks by re-organizing and re-indexing the PROBLEM table during each run. I don't believe this should be neccessary. We normally re-organize and re-index our data each week in our production system after many more transactions than this.
Our systems people state it is our application. Oracle Support tells us the statistics are out of date but have not answered us on why the statistics are out of date and the index is abandoned after 1 run.
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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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