Table spaces

Table space An Oracle database consists of one or more logical storage units called tablespaces, which collectively store all of the database's data. A tablespace is a logical group of data files in a database. A database typically contains at least one tablespace, and usually two or more. Within the database, the tablespace plays a role similar to that of a folder on the hard drive of a computer. Each tablespace in an Oracle database consists of one or more files called datafiles, which are physical structures that obey the rules of the operating system in which Oracle is running.

The size of a tablespace is the size of the datafiles that form the tablespace. The size of a database is the collective size of the tablespaces that constitute the database. It contains tables, indexes, large objects, and long data. It can be used to organize data in a database into logical storage group which is related with where data stored on a system. This tablespaces are stored in database partition groups You can enlarge a database in three ways: Add a datafile to a tablespace Add a new tablespace Increase the size of a datafile

Benefits of tablespaces in database The table spaces are beneficial in database in various ways given as follows: Recoverability: Tablespaces make backup and restore operations more convenient. Using a single command, you can make backup or restore all the database objects in tablespaces. Automatic storage Management: Database manager creates and extends containers depending on the needs. If a user used more storage space, it can be viewed and it is possible to set limits for the storage of the users and so on.  Memory utilization: For increase in the performance of the activities. A single bufferpool can manage multiple tablespaces. You can assign temporary tablespaces to their own bufferpool to increase the performance of activities such as sorts or joins.

Types of Table spaces SYSTEM Table space Data dictionary is an important part in a relational database management system technology. This data dictionary must get stored. This is the place where SYSTEM table space comes in. In order to store the data dictionary tables of Oracle database a table space is created called as system table space. It is also known from the above description that every database has SYSTEM table space necessary.  The data dictionary has information about user name, the privilege of users, roles of users, names and properties of objects like tables, views, synonyms, indexes and so on ,information about constraints created and so on. So data dictionary is an important part in a relational database management system technology. 

There are two options in creating table space There are two options in creating table space. They are namely:  Online Table space : Online table space is one in which the table space created are available to users once the database is opened. Offline Table space : Offline table space on the other hand is one in which the table space created is not available to users . Data Dictionary must be available to users the place of storage of this data dictionary namely the system table space must be created as online table space only. 

Temporary Table space  This is another type of table space which gets created temporarily for users. This table space gets created for each user when the users need to store temporary objects. Thus it is possible to create this temporary table space for each user. 

Default Table space  This gets created when the as soon as the user name gets created and hence the name default table space. For each user name there is an associated default table space. This table space is used when the user does not explicitly provide table space names while creating any object. In such scenarios the default table space is used and gets associated with the object. 

CREATE TABLESPACE Purpose Use the CREATE TABLESPACE statement to create a tablespace, which is an allocation of space in the database that can contain schema objects. create tablespace <tablespace_name>

ALTER TABLESPACE Purpose Use the ALTER TABLESPACE statement to alter an existing tablespace or one or more of its datafiles or tempfiles. Syntax: alter_tablespace::=

Dropping a tablespace Dropping a tablespace is a structural change to the database that requires a backup. The extent size of the objects in the tablespace are subject to the tablespace's minimum extent size.

Database Monitoring Database Monitoring is process of monitoring the performance of databases and providing extensive information so that necessary steps can be taken before a break down of vital business processes occurs. It monitors the activities and metrics (intimations/ messages) related to database health, analyzes the workload running against the database, and automatically identifies any issues that need DBA’s attention as an administrator. The identified issues are either presented as alerts and performance findings in Enterprise Manager or, if you prefer, can be sent to DBA through e-mail.

User Management user management system manages users and their privileges on the DBMS. The User Management service enables to create and manage login credentials for each user. You can also limit the functionality for each user. User Management is an authentication feature that provides administrators with the ability to identify and control the state of users logged into the network. It allows to query and filter users that are currently logged into the network, manually log out users, and control user login counts and login times.

Examples of activities of user management The applications a user can access Whether access is read-only If a user can update information The features a user can access within the Interface, if applicable

User Management functions Contributes to the overall security of your business Makes it easier for your users to access the pages they need Simplifies deployment of services within organisation

Application Programmers They are the developers who interact with the database by means of DML queries. These DML queries are written in the application programs like C, C++, JAVA, Pascal etc. These queries are converted into object code to communicate with the database. For example, writing a C program to generate the report of employees who are working in particular department will involve a query to fetch the data from database. It will include a embedded SQL query in the C Program.

Sophisticated Users They are database developers, who write SQL queries to select/insert/delete/update data. They do not use any application or programs to request the database. They directly interact with the database by means of query language like SQL. These users will be scientists, engineers, analysts who thoroughly study SQL and DBMS to apply the concepts in their requirement. In short, we can say this category includes designers and developers of DBMS and SQL.