Tips to keep your inbox clutter free

1. Delete: Every time you read an email, decide if the information is relevant to you. If not, delete it.

2. Do: If you can do whatever the email is requesting in two minutes, do it there and then.

3. Delegate: If it can't be done in two minutes but you are in a position todelegate it, pass it on to somebody else.

4. Defer: If you can't do the task immediately but it will take longer than two minutes, pick a time when you will get it done and add it to a to-do list.

5. Diminish: Cut down your email load by making rules in your inbox and directing emails into different folders.

6. Daily: Get your unread email count down to zero and do it daily.

Ref: http://timesofindia.indiatimes.com/life-style/relationships/work/6-Ds-to-keep-your-inbox-clutter-free/articleshow/17570989.cms

Command line command to auto kill a command after a certain amount of time

Ref: http://stackoverflow.com/questions/601543/command-line-command-to-auto-kill-a-command-after-a-certain-amount-of-time

( /path/to/slow command with options ) & sleep 5 ; kill $!

This runs the first command, inside the parenthesis, for five seconds, and then kills it. The entire operation runs synchronously, i.e. you won't be able to use your shell while it is busy waiting for the slow command. If that is not what you wanted, it should be possible to add another &.

The $! variable is a Bash built in that contains the process ID of the most recently started subshell. It is important to not have the & inside the parenthesis, doing it that way loses the process ID.

ORACLE Find host name of a currently connected Schema/Instance

This query would give you the server host name of ORACLE machine


 SELECT sys_context('USERENV', 'SERVER_HOST') FROM DUAL;

Oracle: Merge Date between tales OR copy from table to table

Ref:
http://asktom.oracle.com/pls/apex/f?p=100:11:0::::P11_QUESTION_ID:5646797700346972949

You Asked

Hello,

I have a requirement to update 2 columns (A, B) in a arbitrarily (very, very) large table. The values that needs to be updated relies on values from another table and must be consistent with the values from the other table. Since the values in A differ from B, currently, i have to do 2 updates to the table for each record in the cursor. This is obviously inefficient. It can take longer than 12 hours to complete (and has been confirmed as such). There surely must be some way to improve the process. All my reading and trawling the web seems to point to using FETCH, BULK COLLECT and LIMIT etc. Is this the way to go? Can you please perhaps furnish an example?

See the code example below:

declare
CURSOR tran
IS
  SELECT oid, user_account_number FROM user_account001;
BEGIN
  FOR t IN tran
  LOOP
    UPDATE transaction001
    SET payer_account_number = t.user_account_number
    WHERE payer_account_oid  = t.oid;
    UPDATE transaction001
    SET payee_account_number = t.user_account_number
    WHERE payee_account_oid  = t.oid;
  END LOOP;
END;

Thanks!

and we said...

why is this anything more than:

begin

merge into transaction001 t
using user_account001 ua
on ( t.payer_account_oid = ua.oid )
when matched then update set payer_account_number = ua.user_account_number;

merge into transaction001 t
using user_account001 ua
on ( t.payee_account_oid = ua.oid )
when matched then update set payee_account_number = ua.user_account_number;

end;

Oracle: varying elements in IN list(comma separated string)

Ref:  http://asktom.oracle.com/pls/apex/f?p=100:11:0::::P11_QUESTION_ID:110612348061

You can use a bind variable in an IN but I don't think it'll do what you want.  I believe 
you want a string that has the value:

    1, 2, 3

for example (a single variable) to be used in a query like:
  
   select * from t where x in ( :that_variable );

and have all rows returned such that x is in the set of 1, 2, 3.  What would happen 
though is that every row in T such that x = "1, 2, 3" would be returned (if it worked the 
other way -- you would never be able to IN on something with commas in it). 

One 'trick' that works very well on Oracle8.0 and up is to use an object type that is a 
nested table type and a simple parse routine that returns this nested table type given a 
string input.  What I mean is best explained via an example:

ops$tkyte@8i> create or replace type myTableType as table of number;
  2  /
Type created.

ops$tkyte@8i> create or replace function str2tbl( p_str in varchar2 ) return myTableType
  2  as
  3      l_str   long default p_str || ',';
  4      l_n        number;
  5      l_data    myTableType := myTabletype();
  6  begin
  7      loop
  8          l_n := instr( l_str, ',' );
  9          exit when (nvl(l_n,0) = 0);
 10          l_data.extend;
 11          l_data( l_data.count ) := ltrim(rtrim(substr(l_str,1,l_n-1)));
 12          l_str := substr( l_str, l_n+1 );
 13      end loop;
 14      return l_data;
 15  end;
 16  /

Function created.

ops$tkyte@8i> 
ops$tkyte@8i> select * from all_users
  2  where user_id in ( select *
  3    from THE ( select cast( str2tbl( '1, 3, 5, 7, 99' ) as mytableType ) from dual ) )
  4  /

USERNAME                          USER_ID CREATED
------------------------------ ---------- ---------
SYSTEM                                  5 20-APR-99

Understand Classloaders

http://zeroturnaround.com/labs/rebel-labs-tutorial-do-you-really-get-classloaders/

XML to database RDMS table mapping

Ref: http://www.xml.com/pub/a/2001/05/09/dtdtodbs.html

ORACLE Generate Dynamic Data Insert GEN_INSERT_STATEMENT function

Some time back, I have a requirement to pull the data on some server and load into my local Db. The best decoupled way to do that is create insert scripts on server and run them back in local(sure, there will be some key constraints and checks, which I am planning to disable and import data).

I googled for the solution, I just got the solution from http://mahmoudoracle.blogspot.in/2012/07/create-insert-statement-for-table-data.html

Just for quick copy paste, I copied the proc from there and keeping it here.

CREATE OR REPLACE FUNCTION GEN_INSERT_STATEMENT (IN_TABLE_NAME VARCHAR2)  
   RETURN VARCHAR2  
 IS  
   LC$COLS_SELECT     VARCHAR2 (4000);  
   LC$COLS_VALUES     VARCHAR2 (4000);  
   LC$COLOUMN      VARCHAR2 (200);  
   CURSOR LCUR$TAB_COLUMNS (IN_TABLE_NAME VARCHAR2)  
   IS  
     SELECT COLUMN_NAME, DATA_TYPE, COLUMN_ID  
      FROM USER_TAB_COLS  
      WHERE TABLE_NAME = IN_TABLE_NAME  
    ORDER BY COLUMN_ID;  
 BEGIN  
   FOR LREC$TAB_COLUMNS IN LCUR$TAB_COLUMNS (UPPER (IN_TABLE_NAME))  
   LOOP  
    LC$COLS_SELECT :=  
       LC$COLS_SELECT  
      || CASE LREC$TAB_COLUMNS.COLUMN_ID WHEN 1 THEN '' ELSE ',' END  
      || LREC$TAB_COLUMNS.COLUMN_NAME;  
    IF INSTR (LREC$TAB_COLUMNS.DATA_TYPE, 'CHAR') > 0  
    THEN  
      LC$COLOUMN :=  
       '''''''''||' || LREC$TAB_COLUMNS.COLUMN_NAME || '||''''''''';  
    ELSIF INSTR (LREC$TAB_COLUMNS.DATA_TYPE, 'DATE') > 0  
    THEN  
      LC$COLOUMN :=  
       '''TO_DATE(''''''||TO_CHAR(' || LREC$TAB_COLUMNS.COLUMN_NAME  
       || ',''mm/dd/yyyy hh24:mi'')||'''''',''''mm/dd/yyyy hh24:mi'''')''';  
    ELSE  
      LC$COLOUMN := LREC$TAB_COLUMNS.COLUMN_NAME;  
    END IF;  
    LC$COLS_VALUES :=  
       LC$COLS_VALUES  
      || CASE LREC$TAB_COLUMNS.COLUMN_ID WHEN 1 THEN '' ELSE ',' END  
      || '''||DECODE('  
      || LREC$TAB_COLUMNS.COLUMN_NAME  
      || ',NULL,''NULL'','  
      || LC$COLOUMN  
      || ')||''';  
   END LOOP;  
   RETURN  'SELECT ''INSERT INTO '  
      || IN_TABLE_NAME  
      || ' ('  
      || LC$COLS_SELECT  
      || ') VALUES ('  
      || LC$COLS_VALUES  
      || ');'' FROM '  
      || IN_TABLE_NAME  
      || ';';  
 END;  

Let's Now run function for table EMP

 SELECT GEN_INSERT_STATEMENT('EMP') FROM DUAL;  

The output is select statement that we should run it to get insert statement of data.

 SELECT 'INSERT INTO EMP (EMPNO,ENAME,JOB,MGR,HIREDATE,SAL,COMM,DEPTNO) VALUES ('  
     || DECODE (EMPNO, NULL, 'NULL', EMPNO)  
     || ','  
     || DECODE (ENAME, NULL, 'NULL', '''' || ENAME || '''')  
     || ','  
     || DECODE (JOB, NULL, 'NULL', '''' || JOB || '''')  
     || ','  
     || DECODE (MGR, NULL, 'NULL', MGR)  
     || ','  
     || DECODE (  
        HIREDATE,  
        NULL, 'NULL',  
         'TO_DATE('''  
        || TO_CHAR (HIREDATE, 'mm/dd/yyyy hh24:mi')  
        || ''',''mm/dd/yyyy hh24:mi'')')  
     || ','  
     || DECODE (SAL, NULL, 'NULL', SAL)  
     || ','  
     || DECODE (COMM, NULL, 'NULL', COMM)  
     || ','  
     || DECODE (DEPTNO, NULL, 'NULL', DEPTNO)  
     || ');'  
  FROM EMP;  

If we run the previous select statement it will generate inert statement for data existed in table EMP.

 INSERT INTO EMP (EMPNO,ENAME,JOB,MGR,HIREDATE,SAL,COMM,DEPTNO) VALUES (7369,'SMITH','CLERK',7902,TO_DATE('12/17/1980 00:00','mm/dd/yyyy hh24:mi'),800,NULL,20);  
 INSERT INTO EMP (EMPNO,ENAME,JOB,MGR,HIREDATE,SAL,COMM,DEPTNO) VALUES (7499,'ALLEN','SALESMAN',7698,TO_DATE('02/20/1981 00:00','mm/dd/yyyy hh24:mi'),1600,300,30);  
 INSERT INTO EMP (EMPNO,ENAME,JOB,MGR,HIREDATE,SAL,COMM,DEPTNO) VALUES (7521,'WARD','SALESMAN',7698,TO_DATE('02/22/1981 00:00','mm/dd/yyyy hh24:mi'),1250,500,30);  
 INSERT INTO EMP (EMPNO,ENAME,JOB,MGR,HIREDATE,SAL,COMM,DEPTNO) VALUES (7566,'JONES','MANAGER',7839,TO_DATE('04/02/1981 00:00','mm/dd/yyyy hh24:mi'),2975,NULL,20);  
 INSERT INTO EMP (EMPNO,ENAME,JOB,MGR,HIREDATE,SAL,COMM,DEPTNO) VALUES (7654,'MARTIN','SALESMAN',7698,TO_DATE('09/28/1981 00:00','mm/dd/yyyy hh24:mi'),1250,1400,30);  
 INSERT INTO EMP (EMPNO,ENAME,JOB,MGR,HIREDATE,SAL,COMM,DEPTNO) VALUES (7698,'BLAKE','MANAGER',7839,TO_DATE('05/01/1981 00:00','mm/dd/yyyy hh24:mi'),2850,NULL,30);  
 INSERT INTO EMP (EMPNO,ENAME,JOB,MGR,HIREDATE,SAL,COMM,DEPTNO) VALUES (7782,'CLARK','MANAGER',7839,TO_DATE('06/09/1981 00:00','mm/dd/yyyy hh24:mi'),2450,NULL,10);  
 INSERT INTO EMP (EMPNO,ENAME,JOB,MGR,HIREDATE,SAL,COMM,DEPTNO) VALUES (7788,'SCOTT','ANALYST',7566,TO_DATE('04/19/1987 00:00','mm/dd/yyyy hh24:mi'),3000,NULL,20);  
 INSERT INTO EMP (EMPNO,ENAME,JOB,MGR,HIREDATE,SAL,COMM,DEPTNO) VALUES (7839,'KING','PRESIDENT',NULL,TO_DATE('11/17/1981 00:00','mm/dd/yyyy hh24:mi'),5000,NULL,10);  
 INSERT INTO EMP (EMPNO,ENAME,JOB,MGR,HIREDATE,SAL,COMM,DEPTNO) VALUES (7844,'TURNER','SALESMAN',7698,TO_DATE('09/08/1981 00:00','mm/dd/yyyy hh24:mi'),1500,0,30);  
 INSERT INTO EMP (EMPNO,ENAME,JOB,MGR,HIREDATE,SAL,COMM,DEPTNO) VALUES (7876,'ADAMS','CLERK',7788,TO_DATE('05/23/1987 00:00','mm/dd/yyyy hh24:mi'),1100,NULL,20);  
 INSERT INTO EMP (EMPNO,ENAME,JOB,MGR,HIREDATE,SAL,COMM,DEPTNO) VALUES (7900,'JAMES','CLERK',7698,TO_DATE('12/03/1981 00:00','mm/dd/yyyy hh24:mi'),950,NULL,30);  
 INSERT INTO EMP (EMPNO,ENAME,JOB,MGR,HIREDATE,SAL,COMM,DEPTNO) VALUES (7902,'FORD','ANALYST',7566,TO_DATE('12/03/1981 00:00','mm/dd/yyyy hh24:mi'),3000,NULL,20);  
 INSERT INTO EMP (EMPNO,ENAME,JOB,MGR,HIREDATE,SAL,COMM,DEPTNO) VALUES (7934,'MILLER','CLERK',7782,TO_DATE('01/23/1982 00:00','mm/dd/yyyy hh24:mi'),1300,NULL,10);  

Made few changes to above GEN_INSERT_STATEMENT to give insert script for table which have too many columns..

CREATE OR REPLACE FUNCTION GEN_INSERT_STATEMENT (IN_TABLE_NAME VARCHAR2)  
   RETURN CLOB
 IS
   LC$COLS_SELECT     CLOB;
   LC$COLS_VALUES     CLOB;
   LC$COLOUMN      CLOB;

   CURSOR LCUR$TAB_COLUMNS (IN_TABLE_NAME VARCHAR2)
   IS
     SELECT COLUMN_NAME, DATA_TYPE, COLUMN_ID
      FROM USER_TAB_COLS
      WHERE TABLE_NAME = IN_TABLE_NAME
    ORDER BY COLUMN_ID;

 BEGIN

   FOR LREC$TAB_COLUMNS IN LCUR$TAB_COLUMNS (UPPER (IN_TABLE_NAME))
   LOOP

   LC$COLS_SELECT :=
       LC$COLS_SELECT
      || CASE LREC$TAB_COLUMNS.COLUMN_ID WHEN 1 THEN '' ELSE ',' END
      || LREC$TAB_COLUMNS.COLUMN_NAME;

    IF INSTR (LREC$TAB_COLUMNS.DATA_TYPE, 'CHAR') > 0
    THEN

      LC$COLOUMN :=
       '''''''''||' || LREC$TAB_COLUMNS.COLUMN_NAME || '||''''''''';

    ELSIF INSTR (LREC$TAB_COLUMNS.DATA_TYPE, 'DATE') > 0
    THEN

      LC$COLOUMN :=
       '''TO_DATE(''''''||TO_CHAR(' || LREC$TAB_COLUMNS.COLUMN_NAME
       || ',''mm/dd/yyyy hh24:mi'')||'''''',''''mm/dd/yyyy hh24:mi'''')''';

    ELSE

      LC$COLOUMN := LREC$TAB_COLUMNS.COLUMN_NAME;

    END IF;

    LC$COLS_VALUES :=
       LC$COLS_VALUES
      || CASE LREC$TAB_COLUMNS.COLUMN_ID WHEN 1 THEN '' ELSE ',' END
      || '''||DECODE('
      || LREC$TAB_COLUMNS.COLUMN_NAME
      || ',NULL,''NULL'','
      || LC$COLOUMN
      || ')||''';

   END LOOP;

   RETURN  'SELECT ''INSERT INTO '
      || IN_TABLE_NAME
      || ' ('
      || LC$COLS_SELECT
      || ') VALUES ('
      || LC$COLS_VALUES
      || ');'' FROM '
      || IN_TABLE_NAME
      || ';';

 END;




DECLARE
   IN_TABLE_NAME VARCHAR2(100) := 'TABLE_NAME_HERE';
   LC$COLS_SELECT     CLOB;
   LC$COLS_VALUES     CLOB;
   LC$COLOUMN      CLOB;
   CURSOR LCUR$TAB_COLUMNS (IN_TABLE_NAME VARCHAR2)
   IS
     SELECT COLUMN_NAME, DATA_TYPE, COLUMN_ID
      FROM ALL_TAB_COLS
      WHERE TABLE_NAME = IN_TABLE_NAME
    ORDER BY COLUMN_ID;
 BEGIN
   FOR LREC$TAB_COLUMNS IN LCUR$TAB_COLUMNS (UPPER (IN_TABLE_NAME))
   LOOP
   LC$COLS_SELECT :=
       LC$COLS_SELECT
      || CASE LREC$TAB_COLUMNS.COLUMN_ID WHEN 1 THEN '' ELSE ',' END
      || LREC$TAB_COLUMNS.COLUMN_NAME;
    IF INSTR (LREC$TAB_COLUMNS.DATA_TYPE, 'CHAR') > 0
    THEN
      LC$COLOUMN :=
       '''''''''||' || LREC$TAB_COLUMNS.COLUMN_NAME || '||''''''''';
    ELSIF INSTR (LREC$TAB_COLUMNS.DATA_TYPE, 'DATE') > 0
    THEN
      LC$COLOUMN :=
       '''TO_DATE(''''''||TO_CHAR(' || LREC$TAB_COLUMNS.COLUMN_NAME
       || ',''mm/dd/yyyy hh24:mi'')||'''''',''''mm/dd/yyyy hh24:mi'''')''';
    ELSE
      LC$COLOUMN := LREC$TAB_COLUMNS.COLUMN_NAME;
    END IF;
    LC$COLS_VALUES :=
       LC$COLS_VALUES
      || CASE LREC$TAB_COLUMNS.COLUMN_ID WHEN 1 THEN '' ELSE ',' END
      || '''||DECODE('
      || LREC$TAB_COLUMNS.COLUMN_NAME
      || ',NULL,''NULL'','
      || LC$COLOUMN
      || ')||''';
   END LOOP;
   dbms_output.put_line('SELECT ''INSERT INTO '
      || IN_TABLE_NAME
      || ' ('
      || LC$COLS_SELECT
      || ') VALUES ('
      || LC$COLS_VALUES
      || ');'' FROM '
      || IN_TABLE_NAME
      || ';');
 END;
/

Ref: http://mugurel.sumanariu.ro/windows/vista-and-win-7-openvpn-route-problem/

How to fix Open VPN issue: Route addition via IPAPI failed

Please refer above link.


OR

add the following to the end of the configuration (ovpn) file:
--------------------------------------------------------------------------------------------------------

route-method exe
route-delay 2

--------------------------------------------------------------------------------------------------------

Learning How to Learn

Ref : http://java.dzone.com/articles/learning-how-learn

I’d like to talk about three aspects of knowledge: span, depth and connections between the disciplines. I’ve come up with a good metaphor to bring these aspects together, and it looks very to the point. Though, I don’t like metaphors that much, as they’re misleading quite often.

Basically, my metaphor stems from another metaphor according to which people can be broken down into two types. The first type is someone who likes to go over many things in their learning and research. The people of the second type pick just one or two disciplines and dig into them. The first type are foxes, the second type are hedgehogs.

To me, learning looks very much like a geological field research. Imagine that you’re facing a new mysterious continent. You know nothing about it. Of course, you can see mountains, forests, rivers but you have no idea of what’s in there. You don’t know what’s over the horizon, is there a sea, how cold this continent is on the north and what’s the temperature in the south.

The map

So, you start putting the map together. You send expeditions everywhere and you sketch the local maps. Then you drill surface holes to identify the soul texture and composition. Then you discover oil, gold, diamonds, and you start mining.

Learning follows exactly the same scenario. Let’s say you’re studying maths. In the beginning you know very little about it.  Okay, you count to 10, and you see how three red balls are different from five blue balls.  Step by step you’re discovering some new territories. You learn multiplication tables, and you’re amazed as you get to know the real numbers, or as you find out that it’s impossible to divide by zero.  You briefly touch upon differential calculus, and for some unknown reason you learn how to take integrals. By the time you’re 16, you’ve got the map of the nearby territories on your hands, but most likely you have no idea of the set theory, topology and functional analysis. It’s very unlikely that you’ve acquired in-depth knowledge in any of the fields in mathematics. Just scooped and scratched the tidbits off of the surface.

High school doesn’t provide solid knowledge. You only sketch your map at school as you get ready to drill the surface holes.

Connections

Choosing your field can be easy … or difficult. One way or another, there you are at a university. Your teachers rightly assume that you know nothing. The truth is: most of the teachers don’t really care where you start your drilling. They deliver their lectures in a boring or in a fun way, and they rarely put any emphasis on the connections between disciplines. Take physicists: they grab differential calculus and use it to solve their problems. No one cares to trace mathematical analysis to physics and to check if it can be used there. Any given scientific field is an island on your map. For some reason, the common belief states that it’s your job to build bridges between the islands – or at least to set up a ferry service.

Your map abounds in the white patches of seas and oceans that can hardly be drilled, except for the shelf areas.

The islands of knowledge build up clusters as they become one integral whole for you, and instead of the bridge an archipelago emerges. That’s the time when you lay down the foundation for cross-field connections. As these connections take shape, the archipelago transforms into a solid land, good enough to host a highway.  For example, you’ve got this distinct knowledge of what derivatives are, and how they can be applied to mechanics. Bang, there you go, now you definitely see a connection between the motion of bodies and differential calculus.

Why differential calculus is a standalone subject in the school curriculum? Why no one ever says how it can be applied to solving practical tasks?

The contemporary education, at least in this country, does help if you’re set to discover and develop the new islands… but not the new continents. Too little attention is paid to the connections, as well as to the paths and the logic of discoveries.  That’s too bad.

Foxes and Hedgehogs

Back to knowledge span vs. knowledge depth. When you set out to some new field, it’s better to put together a map first, that is, to acquire a span of knowledge. That’s the only way to be able to dig deep into the subject later and identify the spots for drilling.

For example, you learn programming. It’d be stupid to dive straight into the theoretical depths of the artificial intellect or the lambda calculus. It’s equally stupid to rush into some programming language. At the entry level, you need to find out the basics: how programming evolved, what is it for, which branches are available, what are their specifics. Next, it’s about the paradigms, types of programming languages, the platforms, how the platforms relate to each other, what are their development trends. Again, it’s about sketching a map of the continent called “software development” and understanding where to get started with this map. If you’re interested in web development – welcome to the world of JavaScript, functional programming, scripting and markup languages. If you’re more into game development, go ahead and look into AI, strictly typified languages and algorithms. Of course, it doesn’t mean that you can skip all the rest, but that’s the way you identify the spots for deep drilling.

You must be a fox first, to be able to shape-shift into a hedgehog later. That’s the problem of today’s world: it’s much easier to end up being a fox forever, than to become a hedgehog. I feel it myself; it’s a lot harder to get deep down into your chosen field of knowledge.  You always want to read just one more blog post, check Twitter, take a look at this interesting article or book.  When all the world’s information is at your fingertips, it’s soo tempting to be a fox.  

Deep drilling

The spot is selected, and the drill sharpened. So, how to drill now? Watch out for interesting soil layers and horizons. If you reach those layers, you’d never roll back. Beware the space in between the layers – that’s where the rocks might crumble. You dig deep into the subject, you read, you do something, and there’s a moment when things fall into place. Congrats! You’ve found the gold.

There’s one more good metaphor, I’ve picked it up in some book. In the beginning you find yourself in the dark room, and you’re using touch and feel to discover what’s in this room. Then there’s an instant, when the lights turn on, and you see very clearly what is where. The same is going on in your head. The light is suddenly on, and all the standalone concepts get precisely aligned. You will never forget that moment, and this clear alignment will always be there. The lights will be on at all times. The overhead lights might dim with time, but they won’t go out completely.

At times it’s very hard to make yourself keep on drilling. When you see that nothing changes, and you’ve been pecking this subject for several months with no evident progress, you just want to give up everything and get away to some sunny beach. What are you supposed to do in this case? The answer is the same – keep on doing it. If you give up once, give up twice – you’d lose your self-confidence, that’s it. You’d obsess over the thought that you’re good for nothing and get stuck at your current layer forever. You have to keep on drilling. You have to get to the first precious layer and experience the “aha!” moment. You have to turn on the lights to see what’s in the room.

What’s the difference between brilliant programmers and average programmers? It might well be about just one thing: with brilliant programmers, this faith is there all along. They just believe they can’t be anything else but brilliant programmers, whereas average programmers never conjure such things and give up on the drilling eventually. The power of faith and self-confidence can work wonders.

What if you don’t like the drilling location that you’ve previously selected? You have to get busy with something else then. If you take no delight in the studies, if you unconsciously register the count of pages in a new book the moment you open it – this subject or this discipline is not for you. Go over your map one more time and find another location. Maybe you’d get interested in UX, or automation, or marketing. With one or two trial drillings you will locate the spots worth putting your effort into.

Summary

So, how we learn? What should we do to make the learning process more efficient?

1. Turn on “the fox mode” and sketch your map. Identify some starting points for a more in-depth look into the subject.
2. Try to make sense of the connections between disciplines and order the studies logically. It’s quite easy on the high-level.
3. Turn on “the hedgehog mode” and dig deep. You’ll have to interrupt the focused digging though to jump to the related subjects, otherwise you won’t be able to reach the even deeper layers.

A great teacher would disclose his map to the students, guiding their way and showing implicit connections between the disciplines. Students will never lose their way if they have such a map.

Unfortunately, I haven’t come across a teacher who would have done that to his students. So I have to break through the jungle all by myself, working with my machete and carrying my torch, as I put new territories on the map. Hopefully, my children will have better luck.

List all IP addresses connected to your Server

Ref: http://www.techgig.com/skillpage/Java/List-all-IP-addresses-connected-to-your-Server/1063

Below is an Unix command to list all the IP addresses connected to your server on port 80.

netstat -tn 2>/dev/null | grep :80 | awk '{print $5}' | cut -d: -f1 | sort | uniq -c | sort -nr | head

Output – Total connections by IP, from highest to lowest.

 97 114.198.236.100
 56 67.166.157.194
 44 170.248.43.76
 38 141.0.9.20
 37 49.248.0.2
 37 153.100.131.12
 31 223.62.169.73
 30 65.248.100.253
 29 203.112.82.128
 29 182.19.66.187

Note

This command is useful to detect if your server is under attack, and null route those IPs. Read this null route attacker IP story.



Let break above lengthy command into pieces :

1. netstat -tn 2>/dev/null

Uses netstat to list all network connections, ins and outs.

1. -n – Display numeric only, don’t resolve into name.


2. -t – Display only TCP connections.

Output

#Examples - 7 connections
 tcp 0 0 64.91.*.*:80 114.198.236.100:12763 TIME_WAIT 
 tcp 0 0 64.91.*.*:80 175.136.226.244:51950 TIME_WAIT 
 tcp 0 0 64.91.*.*:80 175.136.226.244:51951 TIME_WAIT 
 tcp 0 0 64.91.*.*:23 202.127.210.2:14517 TIME_WAIT 
 tcp 0 0 64.91.*.*:80 149.238.193.121:65268 TIME_WAIT 
 tcp 0 0 64.91.*.*:80 114.198.236.100:44088 ESTABLISHED
 tcp 0 0 64.91.*.*:80 175.136.226.244:51952 TIME_WAIT

2>/dev/null

Redirect all unwanted output to /dev/null, a special place to absorb all output and clear it.

2. grep :80

Only display the IP address that connected to server on port 80.

tcp 0 0 64.91.*.*:80 114.198.236.100:12763 TIME_WAIT 
 tcp 0 0 64.91.*.*:80 175.136.226.244:51950 TIME_WAIT 
 tcp 0 0 64.91.*.*:80 175.136.226.244:51951 TIME_WAIT 
 tcp 0 0 64.91.*.*:80 149.238.193.121:65268 TIME_WAIT 
 tcp 0 0 64.91.*.*:80 114.198.236.100:44088 ESTABLISHED
 tcp 0 0 64.91.*.*:80 175.136.226.244:51952 TIME_WAIT

3. awk ‘{print $5}’

Uses awk to display the 5th field only.

114.198.236.100:12763 
 175.136.226.244:51950
 175.136.226.244:51951
 149.238.193.121:65268
 114.198.236.100:44088
 175.136.226.244:51952

4. cut -d: -f1

Uses cut to extract the content.

1. -d – Character immediately following the -d option is use as delimiter, default is tab.


2. -f – Specifies a field list, separated by a delimiter.

114.198.236.100
 175.136.226.244
 175.136.226.244
 149.238.193.121
 114.198.236.100
 175.136.226.244

5. sort | uniq -c | sort -nr

Sort the list, group it and sort it again in reverse order.


sort

114.198.236.100
 114.198.236.100
 149.238.193.121
 175.136.226.244
 175.136.226.244
 175.136.226.244

uniq -c – Group it.

2 114.198.236.100
 1 149.238.193.121
 3 175.136.226.244

sort -nr – sort by numeric, and reverse order (highest display first)

3 175.136.226.244
 2 114.198.236.100
 1 149.238.193.121

Done.

6. head

This is optional, to display the first 10 result. 

References

1. /dev/null


2. Netstat


3. AWK


4. Cut


5. Uniq


6. Sort

Things Great Engineers (almost) never say

Ref: http://java.dzone.com/articles/things-great-engineers-almost

• “I’ve used _____ but I have no idea how it works” – Great engineers gained their skills through probing and curiosity.  They go ‘under the hood’ of the products they use just to understand how things work, even if that information will never be very useful to them.  It is unclear whether this need to dig deeper is a choice or a compulsion, but it seems that it is a trait of the best talent.
• “______ works, I just don’t know how to explain it” –
• “I will need ______ (tool/condition) to complete this task” –
• “I’ve learned all I want/will ever need to know about ________ “ –
• “There is no solution” –
• “I hate programming” -
• “I’m an expert in _____”
• “I don’t understand the business” –
  
• “I don’t pay particular attention to industry trends” –

How System.currentTimeMillis() works in JAVA

Ref: http://www.ageofcode.com/java-articles/14-how-does-systemgettimeinmilliseconds-work

This article delves into the deceptively simple method System.currentTimeMillis(). It tries to provide some insight into the meaning of the value it returns. In so doing it explains what is meant by the "current time" in Java. It also examines this concept in relation to the timezone and daylight savings configuration of the computer on which it is produced.
The javadoc for the method System.currentTimeMillis() explains the concept exactly; it says that the value is:

"the difference, measured in milliseconds, between the current time and midnight, January 1, 1970 UTC".

I have always found this definition particularly unfriendly and difficult to grasp, it leaves a lot unsaid. If you are unsure about what it means then I believe that the following text may help.
The diagram above represents two time synchronized computers in two different timezones whose "wall" clocks show different times. At the represented moment in time, computer A in America (Atlantic Standard Time) shows 5:00 o'clock in the morning and computer B in Australia (Western Standard Time) shows 4:00 o'clock in the afternoon.
If we were to call System.currentTimeMillis() on both of these computers in the same instant then the values returned from both calls would be theoretically equal to each other. This is shown in the diagram, where the value for System.currentTimeMillis() is the same for both computers
What actually happens is that each of the computers independently calculates what the current date and time is in UTC and then uses the derived value to determine the number of milliseconds which have elapsed since the epoch. Theoretically there is only ever one correct UTC time so they should both arrive at the same answer.
The calculation uses the system clock, the timezone and daylight savings configurations as inputs as well as no doubt taking into account some platform specific factors. Implementations are native so they will definitely vary across platforms and JVMs.
The mistake I used to make, and a mistake I think a lot of people make, is to assume that the System.currentTimeMillis value is provided in terms of the timezone that the computer is in (i.e. wall clock time), rather than in UTC. If this was the case, the value returned by computer B in Australia would be larger than the one returned by computer A in America. This misunderstanding is very damaging as it affects the way one understands the java.util.Date and java.util.Calendar classes too.
If you think about it, the way it actually works makes a lot of sense. It means that we can directly compare the time in milliseconds from two computers regardless of their timezones.
The following table presents the contrived data with the computers in America and Australia in more detail. It also adds some data for a computer in Greenwich in London. The last column indicates whether or not the "Automatically adjust clock for daylight savings changes" option has been set to on or off (This option is available on Windows).
Read More

Is Java Dead or Invincible?

Ref: http://java.dzone.com/articles/java-dead-or-invincible

ORACLE Find SID of a currently connected Schema/Instance

Ref: http://stackoverflow.com/questions/6288122/checking-oracle-sid-and-database-name

The following query is useful to find SID from the connected session.

select sys_context('userenv','instance_name') from dual;

Using JMeter with WebSphere MQ

Ref: http://www.ibm.com/developerworks/websphere/library/techarticles/0808_vandekuil/0808_vandekuil.html

 Looks liks IBM removed the link and the info in that link can be find in below web archive page but without images :(

http://web.archive.org/web/20120110133537/http://www.ibm.com/developerworks/websphere/library/techarticles/0808_vandekuil/0808_vandekuil.html

Introduction
JMeter is frequently used to automate Web site testing, and it can send messages over JMS. This article shows you how to send messages from JMeter to IBM® WebSphere® MQ. This knowledge can help you automate your testing, for example, by enabling you to insert messages into MQ using JMS. WebSphere MQ can then process these messages and expose them through a Web service or an HTML page. With the JMS request, you can test a complete flow without human intervention, as well as schedule tests automatically and collect the results of the test into HTML reports. How does this process work? Here is an overview of the procedure and the tasks involved:

Open Office Macro Horizontal Odd-Even Row Compare

 Sub HorizonatalCompareOddEvenRows()  
   vSelection = ThisComponent.CurrentSelection  
   oSelect=ThisComponent.CurrentSelection.getRangeAddress  
   oSelectColumn=ThisComponent.CurrentSelection.Columns  
   oSelectRow=ThisComponent.CurrentSelection.Rows  
   CountColumn=oSelectColumn.getCount  
   CountRow=oSelectRow.getCount  
  oSelectSC=oSelectColumn.getByIndex(0).getName  
   oSelectEC=oSelectColumn.getByIndex(CountColumn-1).getName  
   oSelectSR=oSelect.StartRow+1  
   oSelectER=oSelect.EndRow+1  
   NoCell=(CountColumn*CountRow)  
   If CountColumn=1 AND CountRow=1 Then  
    MsgBox("Cell " + oSelectSC + oSelectSR + chr(13) + "Cell No = " + NoCell,, "SelectedCells")  
   Else  
    MsgBox("Range(" + oSelectSC + oSelectSR + ":" + oSelectEC + oSelectER + ")" + chr(13) + "Cell No = " + NoCell,, "SelectedCells")   
   End If  
   colorArray = Array(RGB(255,141,6), RGB(255,141,36), RGB(255,141,66), RGB(255,141,96), RGB(255,141,126))  
   colorAraySize = UBound(colorArray)  
 For colIndex = 0 To CountColumn-1  
   For rowIndex = 0 To CountRow-2  
           If (rowIndex mod 2) = 0 Then  
               vSel = vSelection.GetCellbyPosition(colIndex,rowIndex)  
               vNext = vSelection.GetCellbyPosition(colIndex,rowIndex+1)  
               s = vSel.getString()  
               s2 = vNext.getString()  
                 If Len(s) > 0 AND Len(s2) > 0 Then  
                   'Print s, s2, "(",colIndex,",",rowIndex,")","(",colIndex,",",(rowIndex+1),") Comp result",StrComp( s, s2)  
                   If StrComp(s, s2) <> 0 Then  
                    index = rowIndex mod colorAraySize  
                    vNext.CellBackColor = colorArray(index)  
                   Else  
                    'vSel.CellBackColor = RGB(255,255,255)  
                   End If  
                 Else  
                   'Print "Nothing is selected"  
                 End If  
           End If    
   Next  
 Next  
 End Sub  

Application logging guide lines - 2

Ref: http://www.bugfree.dk/blog/2009/07/22/basic-logging-guidelines/

Basic logging guidelines

Next to unit testing I believe in logging to improve the quality of an application. Instrumenting code with logging (or tracing for that matter) should be an integral part of writing production code. Yet, I’ve often found it not to be the case or that what got logged only made sense to the developer who wrote the entry.
Not logging implies that debugging the application outside the development environment is largely based on guesswork. That’s interesting given that most applications spend the majority of their life running outside the development environment.

Life in the sandbox

I suspect the absence or low quality of log statements can be, at least partially, explained by developers not finding them useful during development. The debugger available there is generally inferior to the print-lining approach of logging. That said, I’d argue that many developers don’t concern themselves enough with how their code behaves in a production environment. Rather than investing a small amount of time in adding log statements up-front, their focus is solely on satisfying functional customer requirements.
A related case could be made for exception handling. For instance, rather than asserting the validity of an argument up-front and throwing an appropriate exception, the code may later fail with a NullReferenceException. Not throwing the exception up-front, close to where the actual error occurred, one will have a hard time tracking down the issue. Especially since a stack trace with symbols and line numbers is rarely available in a production environment.
For someone having to resolve the issue, almost any clue as to the cause would be most welcomed. Without a clue that someone would walk around in the dark in the hope of stumbling into a solution.

End users aren’t the only users

As software developers we have to acknowledge that end users aren’t the only users of our software. System administrators, developers, and the like should also be factored in during development. Especially since the cost of instrumenting code at key places, early on, doesn’t add significantly to the overall development cost. Focusing on what can go wrong and communicating it well saves time, money, and frustration down the line. And as a bonus you might create better self-documenting code.
That said it’s important to strike a balance between logging too little and too much information. A log should be detailed enough to reveal patterns of use. Ideally, the log should read like a story with short sentences detailing what’s about to happen, what did or didn’t happen, and possibly why.
I’m not suggesting that we turn logging into a runtime version of literate programming. But simply that sufficient contextual information be provided, i.e., instead of logging “URL = ‘bugfree.dk’”, consider the more elaborate “Retrieving URL for indexing: ‘http://bugfree.dk’”.

Keep your statements clean

On the other hand, log statements shouldn’t be immune to the DRY principle. So make sure to have the logging framework automatically capture common bits of contextual information, such as the date and time of the entry and the class and method within which the log statement originated. On a similar note, don’t explicitly log when a method is entered or existed. Instead, treat such a case as a cross-cutting concern and take an Aspect Oriented approach to logging it.
Lastly, not every method requires (extensive) logging. Figuring out when and what to log is key. Debugging the application, fixing bugs, and experience should provide guidance into what’s useful to log.