Mind maps is a taking note and technique of creative thinking. It helps you to take your notes more creative way, to remember them easier and to understand them more obvious.

This technique is the most suitable method for perception and storage style of brain. Mind maps create a visual picture of informations that save in your brain. With this method your brain hold informations in memory more easier, furthermore it helps you to extract at paper easily. This technique is completely different other working techniques, it enables creative thinking and to be earned time to person. Tony Buzan is the initiator of this technique. Many people pointed out that they have succeeded many subjects like studying lesson, solving problem, writing summary, planning, speaking etc.

You can use colors, shapes, diagrams, pictures, symbols with this technique. Especially using colors is important to release imagination.

There are many advantage of mind maps unlike method of taking traditional linear note.

* To spend less time; note only main words called “key word” and reading

* To appear creative thinking

* To grow remembering power

* To concentrate essential subjects

Mind maps is not static or restrictive. Afterwards it can be made addition or correcting.

Here is How to Make a Mind Map

There is a lot of computer programs and web sites for making a mind map.

Novamind

imindmap , my favorite mind mapping program

Mindmeister , my favorite online mind mapping site

My example that I have made by using mindmeister

In course of time number of application users may increase. And capacity of Oracle servers may be insufficient. At this situation you have to buy additional hardware resources. To buy additional resources means that spend extra money and time. But Oracle Shared Server come to help and it can be stopped your headaches.

You know Oracle database service users via creating server process. As default one server process service only one user process (dedicated server process), one-to-one relationship. But shared server process can service multiple user process, one-to-many relationship. It is a quite useful method for minimizing usage of hardware resources.

Although shared server process is useful method, it cannot be applied to every application type. Which application type is suitable? Applications that have small transactions and that returning small result set are good. Because of number of server processes is limited, dealing bigger result sets reduce response time.

In dedicated server environment an user request assigns to one server process directly. However in shared server environment an request is treated by a dispatcher process.  A dispatcher process is responsible for servicing user requests. It has ability for servicing many ones.

Dispatchers put the requests that coming from user into request queue. The requests prepared by shared server process put into response queue and these are returned the user by dispatcher. Although all dispatchers use same request queue each dispatchers have own response queue.

When being switched dedicated server to shared server , some changes occur in memory structure. The some session informations are holded in PGA are began to be held in SGA. This area is called User Global Area(UGA).

Finally note that Oracle Shared Server is a scalability enhancement option, not a performance enhancement option. This is summary of above explanations.

The theory propounded by James Q. Wilson and George L. Kelling in the beginning of 1980s. It explains with the following example in Wikipedia.

Consider a building with a few broken windows. If the windows are not repaired, the tendency is for vandals to break a few more windows. Eventually, they may even break into the building, and if it’s unoccupied, perhaps become squatters or light fires inside.

Or consider a sidewalk. Some litter accumulates. Soon, more litter accumulates. Eventually, people even start leaving bags of trash from take-out restaurants there or breaking into cars.

By being based on this theory, the authorities that predict much bigger problems can be solved by giving priority to the smallest problems and violations of rule in some big cities as New York provided crime ratioes reduced about zero level within next 20 years.

Broken windows theory can also constitute solution for many big problems at your business life. In your own business or in the company you work, to solve the problems seem unimportant fastly prevents to be repeated failure like them and become bigger problems supported by those small problems.

http://en.wikipedia.org/wiki/Broken_windows

Writing business logic by using PL/SQL is a good opinion to keep in database all things and in terms of security.

On the other hand, do you think that things you can do with PL/SQL is limited with this.

The following web site you maybe give hints about what sort to do much more.

www.plpdf.com

I love PL/SQL…

2. Nested Table

Nested Table is an another collection type. The difference from associative array I mentioned earlier is that need to initialize before using it. Besides nested tables can use as table columns.

CREATE [ OR REPLACE ] TYPE type_name AS | IS TABLE OF element_datatype [ NOT NULL ];

Example;

    DECLARE
        TYPE TEmpLstType IS TABLE OF VARCHAR2 (20);
        emp_list TEmpLstType := TEmpLstType ( );  //  must initialize
    BEGIN
       emp_list.EXTEND;
       emp_list (1) := ‘Mehmet’;
       emp_list.EXTEND (2);
       emp_list (1) := ‘John’;
       emp_list (2) := ‘David’;
       FOR rw IN emp_list.FIRST .. emp_list.LAST
       LOOP
           DBMS_OUTPUT.PUT_LINE (emp_list (l_row));
       END LOOP;
    END;

With EXTEND method, it is opened an empty room in the emp_list nested table.
You can use nested tables as table columns. For example,

       CREATE TYPE TEmpAddresType AS TABLE OF VARCHAR2(100);
    CREATE TABLE employees (
        id NUMBER,
        name VARCHAR2(50),
        address_list TEmpAddresType )
    NESTED TABLE address_list STORE AS address_list_ntable;

The address list will store in the address_list_ntable. address_list_ntable cannot query. If you do, 
          select * from address_list_table;

then oracle will raise “ORA-22812: cannot reference nested table column’s storage table”.

3. VARRAY (variable-sized arrays)

This type are alike nested table. The difference from nested table is that using for small arrays. It can also use as table columns like nested table.

   CREATE [ OR REPLACE ] TYPE type_name AS | IS VARRAY (max_elements) OF element_datatype    [  NOT NULL ];

     CREATE TYPE TEmpAddresVtype IS VARRAY (2) OF VARCHAR2 (100); // have max 100 elements
    CREATE TYPE TEmpBirthdateVtype IS VARRAY (1) OF VARCHAR2 (100);
    CREATE TABLE employees (
         name VARCHAR2(100),
         address_lst TEmpAddresVtype,
         birthdate_lst TEmpBirthdateVtype );

    DECLARE
        address_list   TEmpAddresVtype := TEmpAddresVtype ( );
        birthdate_list TEmpBirthdateVtype := TEmpBirthdateVtype ( );
    BEGIN
        address_list.EXTEND (2);
        address_list (1) := ‘MASLAK/ISTANBUL’;
        address_list (2) := ‘ZEYTINBURNU/ISTANBUL’;
        birthdate_list.EXTEND;
        birthdate_list (1) := ‘01.02.1979′;
        INSERT INTO employees ( name, address_lst, birthdate_lst )
        VALUES ( ‘ahmet’, address_list, birthdate_list );
    END;    

Finally VARRAY and Nested Table are same. But VARRAY is for small arrays and nested table is for big arrays because of storing array elements in background table.

How do you use arrays in PL/SQL?

In other programming language like Java and C# you simply define as following line:
int[] iArray = new int[5];

But in PL/SQL it’s not as easy as that. Why? Because there are three types of collections and we ought to know which collection type must use. Collections are expecially very useful for caching data of lookup tables. If data is cached then amount of context-switching will be less.

There are three types of collections:

1. Associative Array

This type is alike sequential arrays. The difference is that you have not to use sequential index in associative arrays. Index type can be numeric or alphanumeric.

Syntax,

    TYPE table_type_name IS TABLE OF datatype [ NOT NULL ] INDEX BY index_type;

Examples of syntax,

    TYPE startdate_type IS TABLE OF DATE INDEX BY PLS_INTEGER;
    TYPE keyval_type IS TABLE OF NUMBER INDEX BY VARCHAR2(20);   

Code example,

    DECLARE
       TYPE keyval_type IS TABLE OF NUMBER INDEX BY VARCHAR2(20);
       keyval_array keyval_type;
       l_row PLS_INTEGER;
    BEGIN
       keyval_array (’AAA’) := 2;
       keyval_array (’BBB’) := 40;
       keyval_array (’CCC’) := -7;
          DBMS_OUTPUT.put_line ( keyval_array(’AAA’) || keyval_array(’BBB’) || keyval_array (’CCC’) ); 
    END;

Example of for-loop   

    DECLARE
       TYPE keyval_type IS TABLE OF NUMBER INDEX BY VARCHAR2(20);
       keyval_array keyval_type;
       elmnt VARCHAR2(20);
    BEGIN
       keyval_array (’AAA’) := 2;
       keyval_array (’BBB’) := 40;
       keyval_array (’CCC’) := -7;    
       elmnt := keyval_array.FIRST;
       WHILE (elmnt is not null)
       LOOP
         IF keyval_array.EXISTS(elmnt) THEN
           DBMS_OUTPUT.PUT_LINE ( elmnt || ‘=’ ||  keyval_array (elmnt) );
         END IF;
           elmnt := keyval_array.NEXT(elmnt);
       END LOOP;    
    END;

There is various methods you use for associative arrays. Some of these are FIRST/LAST, EXISTS, PRIOR/NEXT, COUNT, DELETE.

At the next post I will try to introduce other two collection types, Nested tables and VARRAYs.