* A few days ago I shared a bit rubbish after graduation learning java and Oracle article, could be determined to enter the IT graduates or people a little help. Many current students email asking how I should be learning Oracle, while the project is now into the last chance of a little free time. Review about Oralce basis points while doing notes, also hope to give colleagues the need to drop in the bucket.
To affirm this: I mentioned here just to get into the basics, but as long learned that a project is enough to meet the general needs. If you would like to develop areas such as DBA, this only the first step is the Great Wall. On the technology I usually defined as: Introduction, understanding, familiar, proficient. China is now the vast majority of PG (certainly including me) Department and the entry and understanding risk. Really hope you were home later on in the near future we can in this regard over India, to catch up with America.
Oracle Introduction (1) must know the technical terms
1: SQL (Structured Query Language) query structure.
2: something (Transaction): refers to as a single logical unit of work performed a series of operations. And the transaction must have four characteristics:
<1>: atomic (atomic): transaction must be atomic unit of work; for its data changes, or all of the implementation or not implementation of the whole.
<2>: consistency (consistent): a transaction is completed, all data must have maintained a consistent state.
<3>: isolation (insulation): the transaction by the concurrent changes to be made with any other concurrent transactions modify the isolation
<4>: Persistence (Duration): transaction is complete, it is for the system of permanent
2: DML, DDL, DCL, TCL operations (division by SQL functions):
(1): Database Manipulation Language: DML (Data Manipulation Language) - include: SELECT, INSERT, UPDATE, DELETE,
MERGE, CALL, EXPLAIN PLAN, LOCK TABLE.
(2): database definition statements: DDL (Data Definition Language) - including: CREATE, ALTER, DROP, TRUNCATE,
(3): Database control statements: DCL (Data Control Language) - include: GRANT, REVOKE
(4): transaction control statements: TCL (Transaction Control) - including: COMMIT, SAVEPOINT, ROLLBACK,
SET TRANSACTION. (Some books included in DML operation will operate within the TCL).
3: database storage structure: physical and logical storage structure storage structure.
(1): the physical storage structure consists of: <1> extension. DBF data files (Data File);
<2> extension>. LOG log file (Redo Log File);
<3> extension. CTL in the control file (Control File);
(2): Logical Storage Structure: Database block (DATA BLOCKS), panel (EXTENT), paragraph (SEGMENT), table space (TABLE SPACES).
Database block: Oracle used to manage the most basic unit of storage space is the smallest logical storage unit.
Panel: a series of contiguous blocks on the physical form of the storage structure, which is the smallest disk unit.
Section: is an independent logical storage structure, according to characteristics can be divided into: data segment, index segment, rollback segment, LOB segment, temporary segment.
Table space: ORACLE user can use the maximum logical storage structure.
4: Memory Architecture (SGA).
Redo log buffer high-speed data buffer large shared pool shared pool (optional)
Other data dictionary data buffer buffer
5: Oracle instance (instance): the memory and the process of regional cooperation as an Oracle instance. The same process can be divided into single and multi-process instance will be practical (MTS).
6: Data Dictionary (DATA DICTIONARY) by Oracle in a series of cases of read-only form the basis of the table and view and save all the basic information on the image.
7: Paradigm (normal form) theory: 1NF, 2NF3NF, BCNF
The first paradigm (1NF): The most simple definition is no repeat of the column.
The second paradigm (2NF): a simple definition is entirely dependent on the primary key attribute.
The third paradigm (3NF): a simple definition is that property is not dependent on other non-primary attributes.
BCNF paradigm (BCNF): 3NF changes, the simple definition does not depend on non-trivial function of the main property.
This argument may have some colleagues in addition to the first, second paradigm to understand things, 3NF, BCNF can not understand the book to see what the actual examples. Personally feel that as long as the master 1NF, and 2NF enough. In practice very few projects to achieve 3NF and BCNF, and in practice we often sacrifice the pursuit of storage space away DML operation efficiency and convenience.
8: dirty (gray) data block (Dirty data block)
Stored in the memory of the original data has been modified, and modified data not yet written to the database.
9: hot data block (Hot data block)
Store the modified data, who are often called hot data block.
10: a database of basic data such as (Data Object): tables, views, sequences, synonyms, triggers, database links and packages, procedures and functions
(1): Table (Table) - DB basic data storage structure.
(2): View (View) - the view is stored in a database query SQL statement, he causes: For security reasons, the view can hide some of the data
(3): Sequence (Sequence) - the only digital out is used to create the database objects, sequences created with the initial value, increment value, maximum value and so on up to 38 integer
(4): synonym (synonym) - refers to other database tables of the database pointer. He has two types: private (private) and public (public). Private synonym is created in the specified mode and only create access to use the model. Public synonyms are specified by the mode of public access to all database schema (user) can access it.
(5): the trigger (trigger) - a special stored procedure, its implementation is not called by the program, not manually start, but by one event to trigger (such as the DML operation)
(6): Database chain and package (database link) - is connected with the remote database storage definition for the check were distributed database environment for remote
(7): Process (Procedure) - is a PL / SQL block, it is stored in the data dictionary application can be invoked, the benefits of using stored procedures is to implement a data security. Authorized users can not direct the application of some form, while the authorized user to perform a process these tables.
(8): function (Function) - and the process, the function also has a parameter, is stored in a database block. The difference is that function can return the value to the caller, you can call them in the SQL statement.
These are the professionals we often hear the term, learning Oracle we have to know the people say "Segment, DDL operations such as" What is meant, to not give a very amateur feel. The following so we can remember to remember, as long as the class of people than some DBA work on, generally will not use:
Database write (DBW0 or DBWn); log written (LGWR); detection point (CKPT); system monitor (SMON); process monitor (PMON); archive (ARCn); recovery (RECO); lock (LCK0); work queue ( SNPn); queue monitor (QMNn); release (Dispatcher Dnnn) server (Snnn); dirty area (Dirty Buffers); Free Zone (Free Buffers); Free Zone (Free Buffers); Reserve (Pinned Buffers) ... ...