Monday 24 September 2012

Web engineering ( 24 Sep. 2012 )



Web server
Web client
Html
Css

Html language was started
To create an web page open notepad and type desired tags than save it as name.html
Than open the saved file in any web browser
Different tags were explained



Example


<html>
<body>
<h1>
</h1>
<title>
</title>
</body>

</html>
 

Example Explained

-          The text between <html> and </html> describes the web page
-          The text between <body> and </body> is the visible page content
-          The text between <title> and </title> is displayed as a title
-          The text between <h1> and </h1> is displayed as a heading
you can change h1 to h6 it will increase the size of text

What is HTML?

HTML is a language for describing web pages.
  • HTML stands for Hyper Text Markup Language
  • HTML is a markup language
  • A markup language is a set of markup tags
  • The tags describes document content
  • HTML documents contain HTML tags and plain text
  • HTML documents are also called web pages

HTML Tags

HTML markup tags are usually called HTML tags
  • HTML tags are keywords (tag names) surrounded by angle brackets like <html>
  • HTML tags normally come in pairs like <b> and </b>
  • The first tag in a pair is the start tag, the second tag is the end tag
  • The end tag is written like the start tag, with a forward slash before the tag name
  • Start and end tags are also called opening tags and closing tags
to insert any tage following is the syntax
<tagname>content</tagname>



Other tags

<a href="url">Link text</a>
                -to paste a link

Example

<a href="http://www.google.com/">Visit google</a> 


<img src="url" alt="some_text">
                -to paste an image. The image should in same folder where the html file is located
      

For further study  www.w3schools.com



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Database Administration ( 24 Sep. 2012 )



Table space
A tablespace is a logical storage unit - multiple application objects (e.g. tables) can be stored in one tablespace. A database can contain multiple tablespaces
Types of table space
1)      Permanent
2)      Temporary
3)      undo.
Different commands relating tablespace were discussed
Select tablespace_name from dba_bablespace;
Create tablespace name1 datafile ‘path of db file‘ size 10m;          
-this will create a tablespace with name and its size will be 10 Mb
Create user myuser identified by abc123 default tablespace name1
            -this will create a user named as myuser and allocate it tablespace
Drop tablespace name1 including contents and datafiles
            -it will delete tablespace having name “ name1 “ and its contents
Create tablespace name1 datafile ‘path of db file‘ size 10m autoextend on next 1m maxsize 20m extent management local
            -it will auto extents the table space 1Mb when 10Mb will full and max it will allow 20Mb
Create temporary tablespace name1temp tempfile\oradata\oraclal\name1\templ.dbf’ size 10m;
            -this will create a temporary tablespace


Alter tablespace name1 rename to nam3;
            -this will change tablespace name
Select tablespace_namae,status from dba_tablespaces
            -this will show whether tablespace is onlin/offline
Alter database datafile ‘path’ autoextend off;
            -this will do status offline
Alter tablespace name4 add datafile ‘path’ name5.dbf size 10m;
            -this will create a new datafile named as name.5 and replace it with name4 file
 



Tablespace
A tablespace is a storage location where the actual data underlying database objects can be kept. It provides a layer of abstraction between physical and logical data,[1] and serves to allocate storage for all DBMS managed segments. (A database segment is a database object which occupies physical space such as table data and indexes.) Once created, a tablespace can be referred to by name when creating database segments.
Tablespaces specify only the database storage locations, not the logical database structure, or database schema. For instance, different objects in the same schema may have different underlying tablespaces. Similarly, a tablespace may service segments for more than one schema.
By using tablespaces, an administrator can control the disk layout of an installation. A common use of tablespaces is to optimize performance. For example, a heavily used index can be placed on a fast SCSI disk. On the other hand, a database table which contains archived data that is rarely accessed could be stored on a less expensive but slower IDE disk.
While it is common for tablespaces to store their data in a filesystem file, a single file must be part of a single tablespace. Some database management systems allow tablespaces to be configured directly over operating-system device entries, called raw devices, providing better performance by avoiding the OS filesystem overheads.
Oracle stores data logically in tablespaces and physically in datafiles associated with the corresponding tablespace.


A tablespace can be online or offline (not accessible), and can contain one or more datafiles, each of which can be online or offline.
There is no relationship between a tablespace and a schema. Objects in the same schema can be in different tablespaces, and a tablespace can hold objects from different schemas.

A tablespace can be set to read-only to eliminate the need to perform backup and recovery of large, static portions of the database.
A tablespace can be set to temporary to optimise the storage of temporary objects.
Tablespaces can use one of two methods to keep track of free and used space: Dictionary-managed or Locally managed - this is chosen when the tablespace is created and cannot be altered at a later date.
Locally Managed Tablespaces (LMT's)

When creating an LMT, the storage parameters NEXT, PCTINCREASE, MINEXTENTS, MAXEXTENTS, and DEFAULT STORAGE are not required (invalid syntax).
An LMT can have either uniform or variable extent sizes. Variable extents are determined automatically by the system. When you create the tablespace, the UNIFORM or AUTOALLOCATE (system-managed) clause specifies the type of allocation.
- For uniform extents, you can specify an extent size or use the default size, which is 1 MB. Temporary tablespaces that manage their extents locally can only use this type of allocation.
- For system-managed extents, you can specify the size of the initial extent and Oracle determines the optimal size of additional extents, with a minimum extent size of 64 KB. This is the default for permanent tablespaces.
When you create a locally managed tablespace using the CREATE TABLESPACE statement, the SEGMENT SPACE MANAGEMENT clause lets you specify how free and used space within a segment is to be managed:
SEGMENT SPACE MANAGEMENT MANUAL - Use free lists for managing free space within segments. Free lists are lists of data blocks that have space available for inserting rows. (This is the default.)

SEGMENT SPACE MANAGEMENT AUTO - Use bitmaps to automatically manage the free space within segments.
CREATE TABLESPACE mytbs1
DATAFILE '/u01/oracle/data/mytbs01.dbf' SIZE 500M
EXTENT MANAGEMENT LOCAL
SEGMENT SPACE MANAGEMENT AUTO;
See also:
dbms_space.space_usage
dba_tablespaces.SEGMENT_SPACE_MANAGEMENT
Temporary Datafiles
Locally managed temporary tablespaces have temporary datafiles (tempfiles), which are similar to ordinary datafiles except that:
- You cannot create a tempfile with the ALTER DATABASE statement.
- You cannot rename a tempfile or set it to read-only.
- Tempfiles are always set to NOLOGGING mode.
- When you create or resize tempfiles, they are not always guaranteed allocation of disk space for the file size specified. On certain file systems (for example, UNIX) disk blocks are allocated not at file creation or resizing, but before the blocks are accessed.
- Tempfile information is shown in the dictionary view DBA_TEMP_FILES and the dynamic performance view V$TEMPFILE, but not in DBA_DATA_FILES or the V$DATAFILE view.
Note: this arrangement enables fast tempfile creation and resizing; however, the disk could run of space later when the tempfiles are accessed.
Dictionary Managed Tablespaces
A tablespace that uses the data dictionary to manage its extents has incremental extent sizes, which are determined by the storage parameters INITIAL, NEXT, and PCTINCREASE. These can be adjusted to control the extent sizes. When additional space is needed, the NEXT and PCTINCREASE parameters determine the sizes of new extents.
System Tablespace
Every Oracle database contains a tablespace named SYSTEM, which Oracle creates automatically when the database is created.
The SYSTEM tablespace always contains the data dictionary tables for the entire database.
All data stored on behalf of stored PL/SQL program units (procedures, functions, packages, and triggers) resides in the SYSTEM tablespace.
The SYSTEM tablespace is always online when the database is open.
Temporary Tablespace
You specify a default temporary tablespace when you create a database, using the DEFAULT TEMPORARY TABLESPACE extension to the CREATE DATABASE statement.
You can drop the default temporary tablespace. If you do, the SYSTEM tablespace will be used as default temporary tablespace. However, in future releases, this might not be allowed. You cannot make the default temporary tablespace permanent or take it offline.
To change a user account to use a non-default temp tablespace
ALTER USER <user_account> SET TEMPORARY TABLESPACE <temp_tbsp>
Transport of Tablespaces between Databases
Moving data by transporting tablespaces can be orders of magnitude faster than either export/import or unload/load of the same data, because transporting a tablespace involves only copying datafiles and integrating the tablespace metadata.
You can move a tablespace from one Oracle database to another (without copying or moving any files) or you can clone (copy) the tablespace.
Transporting tablespaces will only work between databases on the same platform.
When you transport tablespaces you can also move index data, so you do not have to rebuild the indexes after importing or loading the table data.

"…This sense of order is what makes freedom possible. There are 11 political parties in Denmark because there is only one way to eat lunch. You don't eat at your desk or as you drive and you don't walk down the street munching a hot dog. You eat at a table with a napkin and a knife and fork and candle" - Garrison Keillor

For further study click here

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