Linux / Unix : /dev/null Error Redirection and Other /dev files

What is the usage of " command  > /dev/null 2>&1"?

/dev/null  is  a file which takes the input and doesn't print anything in return. /dev/null is kind of a garbage which doesn't have a limit. Therefore we could send anykind of error message in it and not be bothered.

"2" is the STDERR which is standard errors.
"1" is the STDOUT which is standard output.

We have 3 kind of output showed in the screenshot below.

find . -name scripts 2>&1: This command has the purpose of searching a file or folder named scripts. it also tells that all the errors to be showed in the screen


find . -name scripts 2>/dev/null: In here we are sending all the errors to our garbage. With this command we are preventing any kind of errors to be showed in the screen.

find . -name scripts > /dev/null 2>&1: This command all together stops printing the messages on the screen.

What else are there besides /dev/null ?

There are a whole lot of files besides it. Our Reference-1 tells all about it. But we can say that /dev/null is the most used one.




References:
1- /dev files - http://www.linux.org/threads/what-are-those-dev-files.4713/

2-  Standard output - http://www.codecoffee.com/tipsforlinux/articles2/042.html

Oracle E-Business Suite: Concurrent Requests Performance History - Concurrent Request'lerle ilgili İstatistik Performans Bilgisi

Query About Performance Statistics of Concurrent Requests:

This query gives us the count of  daily run concurrents. In addition to that their daily running duration, average running hours and pending hours are also shown. That's how we could diagnose if there had been wrong with the system. In case there was a problem, we could easily detect and investigate the problem on that day or period.

 SELECT TO_CHAR(TRUNC(ACTUAL_START_DATE),'DD-MON-YY DY') STARTDATE,  
 COUNT(*) COUNT, ROUND(SUM(ACTUAL_COMPLETION_DATE - ACTUAL_START_DATE) * 24, 2) RUNNING_HOURS,  
 ROUND(AVG(ACTUAL_COMPLETION_DATE - ACTUAL_START_DATE) * 24, 2) AVG_RUNNING_HOURS,  
 ROUND(SUM(ACTUAL_START_DATE - REQUESTED_START_DATE) * 24, 2) PENDING_HOURS,  
 ROUND(AVG(ACTUAL_START_DATE - REQUESTED_START_DATE) * 24, 2) AVG_PENDING_HOURS  
 FROM APPLSYS.FND_CONCURRENT_PROGRAMS P,APPLSYS.FND_CONCURRENT_REQUESTS R  
 WHERE R.PROGRAM_APPLICATION_ID = P.APPLICATION_ID  
 AND R.CONCURRENT_PROGRAM_ID = P.CONCURRENT_PROGRAM_ID  
 AND R.STATUS_CODE IN ('C','G')  
 AND TRUNC(ACTUAL_COMPLETION_DATE) > TRUNC(SYSDATE-6)  
 AND TO_CHAR(TRUNC(ACTUAL_START_DATE),'DD-MON-YY DY') IS NOT NULL  
 GROUP BY TRUNC(ACTUAL_START_DATE)   
 ORDER BY TRUNC(ACTUAL_START_DATE) ASC;

Reference:

1-http://dbavandana.blogspot.com.tr/2013/06/concurrent-manager-queries.html

Oracle E-Business Suite: SYSADMIN Yetkisinin Verilmesi - Giving The SYSADMIN Responsibility To Users

Her kullanıcıya "sysadmin"  yetkisini verilmesi:

 select user_name, user_id  
 from fnd_user  
 where user_name like '&username'  
 /  
   
 insert into fnd_user_responsibility(  
 USER_ID,  
 APPLICATION_ID,  
 RESPONSIBILITY_ID,  
 LAST_UPDATE_DATE,  
 LAST_UPDATED_BY,  
 CREATION_DATE,  
 CREATED_BY,  
 LAST_UPDATE_LOGIN,  
 START_DATE,  
 DESCRIPTION,  
 WINDOW_WIDTH,  
 WINDOW_HEIGHT,  
 WINDOW_XPOS,  
 WINDOW_YPOS,  
 NEW_WINDOW_FLAG)  
 values (  
 &apps_user_id, -- change this to your APPS user_id and you will have SYSADMIN Responsibility  
 1,  
 20420,  
 sysdate,  
 0,  
 sysdate,  
 1,  
 1060,  
 sysdate,  
 'System Admin',  
 5.896,  
 5.427,  
 -.042,  
 -.24,  
 'R');  

Oracle E-Business Suite: Oracle Application Kurulumu ile ilgili Bilgiler SQL - Application Info SQL

Oracle E-Business Suite Kurulumu ile ilgili bilgileri gösteren script:

 prompt --> Determining information about this Product Group  
   
 select product_group_id, product_group_name, release_name,   
   product_group_type, argument1  
  from fnd_product_groups;  
   
 prompt --> Multi-Org installed?  
 select multi_org_flag from fnd_product_groups;  
   
 prompt --> Uygulamada birden çok dil yüklü mü?  
 select multi_lingual_flag from fnd_product_groups;  
   
 prompt --> Lisanslanmış Ürünler  
   
 select decode(a.APPLICATION_short_name,  
   'SQLAP','AP','SQLGL','GL','OFA','FA',  
   a.APPLICATION_short_name) apps,  
   o.ORACLE_username, fpi.status, fpi.install_group_num,  
   fpi.product_version, fpi.sizing_factor,   
   fpi.tablespace, fpi.index_tablespace, fpi.temporary_tablespace  
 from fnd_oracle_userid o, fnd_application a, fnd_product_installations fpi  
 where fpi.application_id = a.application_id(+)  
  and fpi.oracle_id = o.oracle_id(+)  
 order by 1,2  
 /  
   
 prompt --> Kayıtlı Uygulamalar
   
 select application_id, application_short_name,  
    basepath  
 from fnd_application  
 order by application_id  
 /  
   
 prompt --> Kayıtlı Oracle Schema'larını Bulmak için  
   
 select oracle_id, oracle_username, install_group_num, read_only_flag  
 from fnd_oracle_userid  
 order by 1  
 /  
   
 prompt --> Kurulu olan dilleri bulmak için  
   
 select decode(installed_flag,'I','Installed','B','Base','Unknown')   
   installed_flag,  
   language_code, nls_language from fnd_languages  
 where installed_flag in ('I','B')  
 order by installed_flag  
 /  

Aşağıdaki raporda kurulu uygulamaların düzenli bir şekilde gösterilmesi amacıyla yaratılmıştır.

SELECT report_headings.report_date,  
     report_headings.sid_name,  
     fa.application_id appn_id,  
     decode(fa.application_short_name,  
        'SQLAP', 'AP', 'SQLGL', 'GL', fa.application_short_name ) appn_short_name,  
     substr(fat.application_name,1,50)||  
        decode(sign(length(fat.application_name) - 50), 1, '...') Application,  
     fa.basepath Base_path,  
     fl.meaning install_status,  
     nvl(fpi.product_version, 'Not Available') product_version,  
     nvl(fpi.patch_level, 'Not Available') patch_level,  
     to_char(fa.last_update_date, 'DD-Mon-YY (Dy) HH24:MI') last_update_date,  
     nvl(fu.user_name, '* Install *') Updated_by  
  FROM applsys.fnd_application fa,  
     applsys.fnd_application_tl fat,  
     applsys.fnd_user fu,  
     applsys.fnd_product_installations fpi,  
     apps.fnd_lookups fl,  
     ( SELECT to_char(sysdate, 'DD-Mon-YY HH24:MI') report_date,  
         vd.name sid_name  
       FROM v$database vd ) report_headings   
  WHERE fa.application_id = fat.application_id  
   and fat.language(+) = userenv('LANG')  
   and fa.application_id = fpi.application_id  
   and fpi.last_updated_by = fu.user_id(+)  
   and fpi.status = fl.lookup_code  
   and fl.lookup_type = 'FND_PRODUCT_STATUS'  
 UNION ALL  
 SELECT report_headings.report_date,  
     report_headings.sid_name,  
     fa.application_id,  
     fa.application_short_name,  
     substr(fat.application_name,1,50)||  
        decode(sign(length(fat.application_name) - 50), 1, '...'),  
     fa.basepath,  
    'Not Available',  
    'Not Available',   
    'Not Available',  
     to_char(fa.last_update_date, 'DD-Mon-YY (Dy) HH24:MI'),  
     nvl(fu.user_name, '* Install *')   
  FROM applsys.fnd_application fa,  
     applsys.fnd_application_tl fat,  
     applsys.fnd_user fu,  
        ( SELECT to_char(sysdate, 'DD-Mon-YY HH24:MI') report_date,  
          vd.name sid_name  
       FROM v$database vd ) report_headings   
  WHERE fa.application_id = fat.application_id  
   and fat.language(+) = userenv('LANG')  
   and fa.last_updated_by = fu.user_id(+)  
   and fa.application_id not in   
     ( SELECT fpi.application_id  
       FROM applsys.fnd_product_installations fpi )  
  ORDER by 5 

Referanslar:

1-http://www.piper-rx.com/pages/reports_free/fadm001_10.trd

Veritabanında En Sık Erişilen Tablolar

Tabloların ne kadar kullanılıp kullanılmadığını görmek için ve bazı gereken veya gerekmeyen tablolarla ilgili bir öngörü oluşturmak için bazen hangi tabloların ne kadar erişildiğini görmek gerekebilir. Bunun için de V$SQL_PLAN tablosu iyi bir referans sağlayabilir.

V$SQL_PLAN içindeki bağlantılar zamanla eskiyeceği için bu sorgudan gelen değerler değişecektir.

SELECT   COUNT (*), object_name
   FROM v$sql_plan
  WHERE operation = 'TABLE ACCESS'
  --and object_name='%%'
GROUP BY object_name
ORDER BY COUNT (*) DESC;

Oracle Veritabanı: Bir Tabloda veya Tablespace'de Bulunan İndex'ler

Bir tablonun üzerinde bazen hangi index'lerin olduğunu bazen merak edebiliriz. Veritabanında yer kaplayan nesnelerle ilgili rapor yaparken bu konu ilgimi çekti. Sileceğim tabloların herhangi birisinin üzerinde index var mı yok mu, hangileri üzerinde hangi index'ler tanımlanmış, bunu öğrenmek istedim. Bunun içinde aşağıdaki gibi bir sorgu kullandım. Bununla ilgili kullandığım ana tablo dba_ind_columns idi.

  Select index_owner, table_name, index_name, column_name  
  FROM dba_ind_columns  
  Where index_owner='BERKE'  
  Order by index_owner, table_name, column_name;  

Peki invalid olan index'ler nasıl bulunabilinir?

Aşağıdaki sorgular ile hangi index'lerin invalid olduğunu bulabiliriz.

select * from dba_indexes where status ='INVALID';  
   
 select * from dba_objects where object_type='INDEX' and status ='INVALID'; 

Invalid olanları bulduktan sonra nasıl rebuild edebiliriz?

Index rebuild etmenin sorgusu görece kolaydır; ancak sorgu çalıştırılmadan önce index'in size'ı ölçülmelidir. Bu sayede index rebuild sorgumuza hem fazladan argüman koyulup koyulmaması gerektiği görülür hem de vereceğimiz sorgunun ne kadar süreceği tahmin edilebilinir.

alter index  rebuild online;;  
   
 veya   
   
 alter index  rebuild;  

Index'ler ne zaman rebuild edilmelidir, nelere dikkat edilmelidir?

Index'ler genellilkle yeni data'lar eklendiğinde veya data'lar silindiğinde değişikliklerin etki etmesi için rebuild edilmelidir.

Buna istinaden yine index performansı düşük olanlara ve büyük dml işlemleri yapılan tablolardaki indexlere rebuild işlemi uygulanır.

Index Rebuild Performansı

Index'lerde rebuild edilmeden önce index size'ına bakılmalıdır; çünkü büyük index'ler rebuild edildiğinde uzun süre database resource'u tüketebilir.

select segment_name,(bytes)/1024/1024 as "MB",(bytes)/1024/1024/1024 as "GB" from dba_segments where segment_type='INDEX' order by "MB" desc; 

Eğer büyük index'ler rebuild edilmek isteniyorsa NOLOGGING argümanıyla çalıştırılmalıdır.

Ayrıca index'ler PARALLEL argümanıyla çalıştırılırlarsa çalıştırılma performansı artar, index rebuild hızlanır.

Index Monitoring:

Index monitoring ile bir index'in kullanılıp kullanılmadığını bulabiliriz. Her ne kadar index monitörleme işi ile database üzerine bir yük eklesek de kullanılmayan index'leri bulup silmek bize yer kazandırabilir.

Monitor başlatma ve bitirme:

 ALTER INDEX indexa MONITORING USAGE;  
 ALTER INDEX indexa NOMONITORING USAGE;  

Monitörlenen index'leri bulma:

 SELECT index_name,  
     table_name,  
     monitoring,  
     used,  
     start_monitoring,  
     end_monitoring  
 FROM  v$object_usage  
 WHERE index_name = 'indexa'  
 ORDER BY index_name; 

Referans:
http://richardfoote.wordpress.com/category/index-rebuild/
http://jonathanlewis.wordpress.com/2009/06/05/online-rebuild/
http://docs.oracle.com/cd/B28359_01/server.111/b28310/indexes003.htm#ADMIN11722
http://www.dba-oracle.com/t_scheduling_oracle_index_rebuilding.htm
http://www.dba-oracle.com/t_index_rebuilding_issues.htm
http://www.oracle-base.com/articles/10g/index-monitoring.php