I have OEl 5.5 installed and patched. I have my SSD mounted..
but when i ran the command 'alter system set db_flash_cache_file ='/media/ssd/' scope=spfile;'
It wouldn't startup giving ORA-01078: failure in processing system parameters...
Is db_cache_advice = ON still necessary when sga_target is set?
View 2 Replies View RelatedConsidering the below factors, I am planning to increase the buffer cache value from 256Mb to 512Mb.
1. Buffer cache hit ratio value is around 35% even in the normal period.
2. free buffer requested value is below during peak & normal hours below.
Statistic Total per Second per Trans
--------------------------------- ------------------ -------------- ------------
free buffer requested 54,694,995 15,226.9 2,523.7
free buffer requested 23,412,674 6,501.7 2,585.9
3. most of the top 5 physical reads & logical reads queries are well tuned and some of queries are doing FTS on small tables (table count min 1500 max 35000). SO indexing option is not required for these queires. But these queries getting executed frequently.
SQL> show sga
Total System Global Area 2148534928 bytes
Fixed Size 731792 bytes
Variable Size 1879048192 bytes
Database Buffers 268435456 bytes
Redo Buffers 319488 bytes
5.top 5 waitevents during db slow performance & high cpu utilization (>80%) issue.
Top 5 Timed Events
~~~~~~~~~~~~~~~~~~ % Total
Event Waits Time (s) Ela Time
-------------------------------------------- ------------ ----------- --------
latch free 1,848,898 153,793 52.00
buffer busy waits 395,280 87,201 29.49
db file scattered read 3,488,648 34,199 11.56
enqueue 4,052 10,897 3.68
CPU time 5,567 1.88
6. Top 5 waitvents during normal activities and CPU utilization is around 40%.
Top 5 Timed Events
~~~~~~~~~~~~~~~~~~ % Total
Event Waits Time (s) Ela Time
-------------------------------------------- ------------ ----------- --------
CPU time 1,860 45.32
db file scattered read 1,133,669 985 23.99
imm op 776 605 14.73
sbtinfo2 208 139 3.40
sbtbackup 2 123 3.00
1) Is shutting down the DB flush all the data buffers, from the buffer Cache?
2) In any oracle version, do we have any way to flush only the buffer Cache.
I have some confusion about Keep Pool in Buffer Cache.
1. What is the reasoning for placing a table in the KEEP buffer pool because if it is frequently accessed, it will be around when needed (ie if it is constantly being accessed it will not age out) .
2. Would the table be still in the Default Pool if the Keep Pool is not sized and the command is being issued alter TABLE SCOTT.EMP storage (buffer_pool keep) ?
3. If the database is restarted will the table be wiped out of the Keep Pool and again be pinned to the Keep Pool ?
In order to improve the performance of our live server, I am trying to do an exhaustive comparison with our test environment which is quite quick in spite of the fact that we port the data from Live every month.
There are no obviously slow queries appearing in the the top SQLs of AWR, we have optimised such things already. Right now it is about general uplift rather than SQL based tuning.
I picked up random SQLs and I noticed a marked differences in the execution time. Typically they are 3 to 4 times and there are cases much more than that.
1. I observed that, while the explain plan of the queries are same, trace of the queries give a different picture. I have observed that the recursive calls, consistent gets and sorts(memory) are quite high on Live.
2. I have no solid reasons to say this but my instincts tell me that the recursive calls is the major contributing factor. It is sometimes 2000+ for an SQL.
3. On googling more on that, it finally made me compare the data dictionary on the AWR report of test and Live.
The dc_objects caught my eyes. In that 4 hour AWR, there were about 10 million get requests and the pct miss was ~10. For similar load, the test server had 5 million gets with 0.08 PCT miss for 4 hours.
11.2.0.2.0
OEL.
Design stage of New SAN. I can put a lot of the database, including redo on SSD.
1. Hardware sub tiering enabled. Has anyone ever gauged performance with enabling 11g Smart flash cache using the SSD as the flash device even with the hardware subtiering on? ie, if the hardware subtiering is moving hotblocks to most performant disk, is there much significant benefit having the flash cache on. Im guessing yes as the flash cache is working at the SGA level.
2. To redo or not to redo on SSD. Many notes say not to so as to avoid log file sync waits. Is there a way to keep it on the SSD and avoid the waits? Is there any risk of enhanced degradation of the disks over time with having so much sequential writes from the redo if I leave it on there?
How to Minimise Waits for 'Log File Sync' [ID 857576.1] (discusses keeping redo off ssd but only generally)
[URL]
In an OLTP environment what cursor_sharing setting is preferred?Though typically we retain the original setting for most of the parameters except memory settings etc. I have queries in the following context
No. I am not facing any issue as of now (I am not supporting any Live environment) But I want to know the desgn considerations
First of all in OLTP environment (say one I am referring) we use pl/sql variables which are obviously bind variables Only in case where plan is expected to change we use hard coded values like 'CREDIT' or 'DEBIT' etc. for acc_type column
Again there can be 2 scenario
1) we use the same query for both acc_type values
2) we use 2 different queries
IF v_parameter = 'CR'
select * from accounts where acc_type='CREDIT'...
else
select * from accounts where acc_type='DEBIT'...
end if;
Again suppose the values are skewed and we gather stats with histograms hereIs't it the setting 'cursor_sharing=similar' which will be useful in above case?as with this setting optimizer will 'think' which plan to pick depending upon the values and bind variable peeking is taken care in option 2 above with IF ELSE clause?
BTW
I have carried several tests but not getting conclusive results For example I created following table with skewed data, created index and gather stats with histogram
SQL> select object_id,count(*) from skewed_data_tab group by object_id;
OBJECT_ID COUNT(*)
---------- ----------
5 30
6 2970
7 10797
8 150000
9 300000
SQL> create index i_skewed_tab_data on skewed_data_tab(object_id);
SQL> exec dbms_stats.gather_table_stats(user,'SKEWED_DATA_TAB',cascade=>true,
method_opt=>'for all columns size 254');
Then traced with following options
1) alter session set events '10046 trace name context forever, level 12';
SQL> begin
for i_outer in(select n from ids order by tstamp)
loop
for i_inner in (select /* for exact */ object_id,object_name,object_type
from skewed_data_tab where object_id=i_outer.n)
[code]...
2) set termout off
alter session set events '10046 trace name context forever, level 12';
@/u04/scripts/exact.sql 5
cat /u04/scripts/exact.sql
select /* for exact */ object_id,object_name,object_type from skewed_data_tab where object_id=&1;
But not getting consistent results
I am currently in the favorable situation in which I have excess amounts of memory available on the database server - a single node setup. The server only serves the single instance and no other processing. Database size is around 2.3tb and memory is 50gb. For the majority of processing, AIX is allocating a significant amount (anywhere from 30-40%) of the memory to the AIX file system cache (persistent pages).
I've been trying to find documentation about this, but have not had any luck yet. My guess is that it would be better to allow Oracle to cache this data - meaning increase the SGA target and max size to allow for a larger buffer cache. However, the nice thing about the AIX cache is if process memory is needed, the file system cache gives up pages. If the memory was allocated to the SGA, its pretty much locked in.
I have read several articles stating that a larger buffer cache is not always better, as a larger cache takes more management. But having both of the caches active seem to be a waste of memory, effectively storing the data twice - once in AIX persistent pages and a second time in Oracle database buffer cache.
I'm trying to demonstrate the working of the OCI client result cache. I've set some parameters,orcl> sho parameter result_cache
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
client_result_cache_lag big integer 3000
client_result_cache_size big integer 1000000
result_cache_max_result integer 5
result_cache_max_size big integer 1984K
result_cache_mode string FORCE
result_cache_remote_expiration integer 0
If I understand the docs correctly, that should be all that is needed.I've complied and run the cdemoqc and cdemoqc2 OCI demos, but I never get anything in the V$CLIENT_RESULT_CACHE_STATS or CLIENT_RESULT_CACHE_STATS$ views. This is probably because the sessions exit after running the queries.
So I've also tried repeating arbitrary queries through cdemo2, which gives a persistent session, but there is still nothing in those views and furthermore the v$result_cache_objects.scan_count for my queries keeps increasing. So I don't think think the client side cache is working.
Is there any relationship b/w tuning BUFFER CACHE and BUFFER BUSY WAITS?
1) Buffer Busy Waits are happening as the User process found the same Datablock is being used by another user in the BUFFER CACHE.
2) And also happens, when the server process found the same Datablock are being used in the Datafile.
i am testing a proc after tuning it but the problem is, it is taking a very very less time which it shouldn't. I know that it is because of the buffer cache and the shared pool. that why i need to clean the cache to retest it.
I cannot bounce the database as other schemas are part of it. so is there any way to clean the cache for that particular schema i.e bouncing any particular schema(i know that the term is not appropriate).
Despite it being one of the major selling points of Exadata (especially from X3 onwards), I'm struggling to find much information on our usage of the Exadata Smart FlashCache (I'm running RDBMS 11.2.0.2 BP7 on a V2 quarter-rack).
I can verify usage of the FlashCache by checking whether the object has been 'pinned' to the FlashCache via DBA_SEGMENTS and I can check for FlashCache usage by querying gv$sysstat (and even v$mystat), but are there other views that I could use? It seems a bit strange for Oracle not to provide the DBA all that much insight into their usage of this feature...
I have a question regarding memory parameters in oracle database 9.2.0.8, especially sga_max_size and db_cache_size. Database server has 32G of ram. Oracle parameter on server shmmax is set to 16G. Is reasonable to set sga_max_size to the same value, and db_cache_size to 80% of that size?
View 2 Replies View RelatedWhat value should i set for sga_target in my oracle 10g database?
Currently -
sga_max_size = 32GB
pga_aggregate_target = 6GB
RAM on server = 64 GB
I'll need to disable db_block_buffers parameters in order to enable sga_target. right?
I am setting the oracle_home,oracle_sid on windows server2008.
oracle client 10g and oracle server 11.2.0.1.0 are installed on my machine and i have created 2 database on my machine.
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?
What is the difference between cache fusion and Cache Coherency. Both are same or different functionality.
View 1 Replies View RelatedI have some question.
TTversion : TimesTen Release 11.2.2.3.0 (64 bit Linux/x86_64) (tt112230:53376) 2012-05-24T09:20:08Z
We are testing a AWT cache group ( with CacheAwtParallelism=4 ).
Application(1 process) to the DML generates to TimesTen(DSN=TEST).
At this point, Are delivered to the 4 parallel DML?
[TEST]
Driver=/home/TimesTen/tt112230/lib/libtten.so
DataStore=/home/TimesTen/DataStore/TEST/test
PermSize=1024
TempSize=512
PLSQL=1
[code].......
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].....
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'.
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?
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 ?
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?
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?
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.
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.
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?
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]...
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.
View 10 Replies View Related