Overview of Importants Features

Overview of High Availability Features

Computing environments configured to provide nearly full-time availability are known as high availability systems. Such systems typically have redundant hardware and software that makes the system available despite failures. Well-designed high availability systems avoid having single points-of-failure.
When failures occur, the fail over process moves processing performed by the failed component to the backup component. This process remasters systemwide resources, recovers partial or failed transactions, and restores the system to normal, preferably within a matter of microseconds. The more transparent that fail over is to users, the higher the availability of the system.
Oracle has a number of products and features that provide high availability in cases of unplanned downtime or planned downtime. These include Fast-Start Fault Recovery, Real Application Clusters, Recovery Manager (RMAN), backup and recovery solutions, Oracle Flashback, partitioning, Oracle Data Guard, LogMiner, multiplexed redo log files, online reorganization. These can be used in various combinations to meet specific high availability needs.

Overview of Business Intelligence Features

This section describes several business intelligence features.

Data Warehousing

A data warehouse is a relational database designed for query and analysis rather than for transaction processing. It usually contains historical data derived from transaction data, but it can include data from other sources. It separates analysis workload from transaction workload and enables an organization to consolidate data from several sources.
In addition to a relational database, a data warehouse environment includes an extraction, transportation, transformation, and loading (ETL) solution, an online analytical processing (OLAP) engine, client analysis tools, and other applications that manage the process of gathering data and delivering it to business users.

Extraction, Transformation, and Loading (ETL)

You must load your data warehouse regularly so that it can serve its purpose of facilitating business analysis. To do this, data from one or more operational systems must be extracted and copied into the warehouse. The process of extracting data from source systems and bringing it into the data warehouse is commonly called ETL, which stands for extraction, transformation, and loading.

Materialized Views

A materialized view provides access to table data by storing the results of a query in a separate schema object. Unlike an ordinary view, which does not take up any storage space or contain any data, a materialized view contains the rows resulting from a query against one or more base tables or views. A materialized view can be stored in the same database as its base tables or in a different database.
Materialized views stored in the same database as their base tables can improve query performance through query rewrites. Query rewrite is a mechanism where Oracle or applications from the end user or database transparently improve query response time, by automatically rewriting the SQL query to use the materialized view instead of accessing the original tables. Query rewrites are particularly useful in a data warehouse environment.

Bitmap Indexes in Data Warehousing

Data warehousing environments typically have large amounts of data and ad hoc queries, but a low level of concurrent database manipulation language (DML) transactions. For such applications, bitmap indexing provides:

• Reduced response time for large classes of ad hoc queries
  
• Reduced storage requirements compared to other indexing techniques
  
• Dramatic performance gains even on hardware with a relatively small number of CPUs or a small amount of memory
  
• Efficient maintenance during parallel DML and loads
  

Fully indexing a large table with a traditional B-tree index can be prohibitively expensive in terms of space because the indexes can be several times larger than the data in the table. Bitmap indexes are typically only a fraction of the size of the indexed data in the table.

Table Compression

To reduce disk use and memory use (specifically, the buffer cache), you can store tables and partitioned tables in a compressed format inside the database. This often leads to a better scaleup for read-only operations. Table compression can also speed up query execution. There is, however, a slight cost in CPU overhead.

Parallel Execution

When Oracle runs SQL statements in parallel, multiple processes work together simultaneously to run a single SQL statement. By dividing the work necessary to run a statement among multiple processes, Oracle can run the statement more quickly than if only a single process ran it. This is called parallel execution or parallel processing.
Parallel execution dramatically reduces response time for data-intensive operations on large databases, because statement processing can be split up among many CPUs on a single Oracle system.

Analytic SQL

Oracle has many SQL operations for performing analytic operations in the database. These include ranking, moving averages, cumulative sums, ratio-to-reports, and period-over-period comparisons.

OLAP Capabilities

Application developers can use SQL online analytical processing (OLAP) functions for standard and ad-hoc reporting. For additional analytic functionality, Oracle OLAP provides multidimensional calculations, forecasting, modeling, and what-if scenarios. This enables developers to build sophisticated analytic and planning applications such as sales and marketing analysis, enterprise budgeting and financial analysis, and demand planning systems. Data can be stored in either relational tables or multidimensional objects.
Oracle OLAP provides the query performance and calculation capability previously found only in multidimensional databases to Oracle's relational platform. In addition, it provides a Java OLAP API that is appropriate for the development of internet-ready analytical applications. Unlike other combinations of OLAP and RDBMS technology, Oracle OLAP is not a multidimensional database using bridges to move data from the relational data store to a multidimensional data store. Instead, it is truly an OLAP-enabled relational database. As a result, Oracle provides the benefits of a multidimensional database along with the scalability, accessibility, security, manageability, and high availability of the Oracle database. The Java OLAP API, which is specifically designed for internet-based analytical applications, offers productive data access.

Data Mining

With Oracle Data Mining, data never leaves the database — the data, data preparation, model building, and model scoring results all remain in the database. This enables Oracle to provide an infrastructure for application developers to integrate data mining seamlessly with database applications. Some typical examples of the applications that data mining are used in are call centers, ATMs, ERM, and business planning applications. Data mining functions such as model building, testing, and scoring are provided through a Java API

Partitioning

Partitioning addresses key issues in supporting very large tables and indexes by letting you decompose them into smaller and more manageable pieces called partitions. SQL queries and DML statements do not need to be modified in order to access partitioned tables. However, after partitions are defined, DDL statements can access and manipulate individuals partitions rather than entire tables or indexes. This is how partitioning can simplify the manageability of large database objects. Also, partitioning is entirely transparent to applications.
Partitioning is useful for many different types of applications, particularly applications that manage large volumes of data. OLTP systems often benefit from improvements in manageability and availability, while data warehousing systems benefit from performance and manageability.

Overview of Content Management Features

Oracle includes datatypes to handle all the types of rich Internet content such as relational data, object-relational data, XML, text, audio, video, image, and spatial. These datatypes appear as native types in the database. They can all be queried using SQL. A single SQL statement can include data belonging to any or all of these datatypes.

XML in Oracle

XML, eXtensible Markup Language, is the standard way to identify and describe data on the Web. Oracle XML DB treats XML as a native datatype in the database. Oracle XML DB offers a number of easy ways to create XML documents from relational tables. The result of any SQL query can be automatically converted into an XML document. Oracle also includes a set of utilities, available in Java and C++, to simplify the task of creating XML documents.
Oracle includes five XML developer's kits, or XDKs. Each consists of a standards-based set of components, tools, and utilities. The XDKs are available for Java, C, C++, PL/SQL, and Java Beans.

LOBs

The LOB datatypes BLOB, CLOB, NCLOB, and BFILE enable you to store and manipulate large blocks of unstructured data (such as text, graphic images, video clips, and sound waveforms) in binary or character format. They provide efficient, random, piece-wise access to the data.

Oracle Text

Oracle Text indexes any document or textual content to add fast, accurate retrieval of information. Oracle Text allows text searches to be combined with regular database searches in a single SQL statement. The ability to find documents based on their textual content, metadata, or attributes, makes the Oracle Database the single point of integration for all data management.
The Oracle Text SQL API makes it simple and intuitive for application developers and DBAs to create and maintain Text indexes and run Text searches.

Oracle Ultra Search

Oracle Ultra Search lets you index and search Web sites, database tables, files, mailing lists, Oracle Application Server Portals, and user-defined data sources. As such, you can use Oracle Ultra Search to build different kinds of search applications.

Oracle interMedia

Oracle interMedia provides an array of services to develop and deploy traditional, Web, and wireless applications that include image, audio, and video in an integrated fashion. Multimedia content can be stored and managed directly in Oracle, or Oracle can store and index metadata together with external references that enable efficient access to media content stored outside the database.

Oracle Spatial

Oracle includes built-in spatial features that let you store, index, and manage location content (assets, buildings, roads, land parcels, sales regions, and so on.) and query location relationships using the power of the database. The Oracle Spatial Option adds advanced spatial features such as linear reference support and coordinate systems.

Overview of Security Features

Oracle includes security features that control how a database is accessed and used. For example, security mechanisms:

• Prevent unauthorized database access
• Prevent unauthorized access to schema objects
• Audit user actions

Associated with each database user is a schema by the same name. By default, each database user creates and has access to all objects in the corresponding schema.
Database security can be classified into two categories: system security and data security.
System security includes the mechanisms that control the access and use of the database at the system level. For example, system security includes:

• Valid user name/password combinations
• The amount of disk space available to a user's schema objects
• The resource limits for a user

System security mechanisms check whether a user is authorized to connect to the database, whether database auditing is active, and which system operations a user can perform.
Data security includes the mechanisms that control the access and use of the database at the schema object level. For example, data security includes:

• Which users have access to a specific schema object and the specific types of actions allowed for each user on the schema object (for example, user SCOTT can issue SELECT and INSERT statements but not DELETE statements using the employees table)
  
• The actions, if any, that are audited for each schema object
  
• Data encryption to prevent unauthorized users from bypassing Oracle and accessing data
  

Security Mechanisms

The Oracle database provides discretionary access control, which is a means of restricting access to information based on privileges. The appropriate privilege must be assigned to a user in order for that user to access a schema object. Appropriately privileged users can grant other users privileges at their discretion.
Oracle manages database security using several different facilities:

• Authentication to validate the identity of the entities using your networks, databases, and applications
  
• Authorization processes to limit access and actions, limits that are linked to user's identities and roles.
  
• Access restrictions on objects, like tables or rows.
  
• Security policies
  
• Database auditing
  
  
  

  Overview of Data Integrity and Triggers

  Data must adhere to certain business rules, as determined by the database administrator or application developer. For example, assume that a business rule says that no row in the inventory table can contain a numeric value greater than nine in the sale_discount column. If an INSERT or UPDATE statement attempts to violate this integrity rule, then Oracle must undo the invalid statement and return an error to the application. Oracle provides integrity constraints and database triggers to manage data integrity rules.
  
  

  Integrity Constraints

  An integrity constraint is a declarative way to define a business rule for a column of a table. An integrity constraint is a statement about table data that is always true and that follows these rules:
  
• If an integrity constraint is created for a table and some existing table data does not satisfy the constraint, then the constraint cannot be enforced.
  
• After a constraint is defined, if any of the results of a DML statement violate the integrity constraint, then the statement is rolled back, and an error is returned.
  

Integrity constraints are defined with a table and are stored as part of the table's definition in the data dictionary, so that all database applications adhere to the same set of rules. When a rule changes, it only needs be changed once at the database level and not many times for each application.
The following integrity constraints are supported by Oracle:

• NOT NULL: Disallows nulls (empty entries) in a table's column.
  
• UNIQUE KEY: Disallows duplicate values in a column or set of columns.
  
• PRIMARY KEY: Disallows duplicate values and nulls in a column or set of columns.
  
• FOREIGN KEY: Requires each value in a column or set of columns to match a value in a related table's UNIQUE or PRIMARY KEY. FOREIGN KEY integrity constraints also define referential integrity actions that dictate what Oracle should do with dependent data if the data it references is altered.
  
• CHECK: Disallows values that do not satisfy the logical expression of the constraint.
  

Keys

Key is used in the definitions of several types of integrity constraints. A key is the column or set of columns included in the definition of certain types of integrity constraints. Keys describe the relationships between the different tables and columns of a relational database. Individual values in a key are called key values.
The different types of keys include:

• Primary key: The column or set of columns included in the definition of a table's PRIMARY KEY constraint. A primary key's values uniquely identify the rows in a table. Only one primary key can be defined for each table.
  
• Unique key: The column or set of columns included in the definition of a UNIQUE constraint.
  
• Foreign key: The column or set of columns included in the definition of a referential integrity constraint.
  
• Referenced key: The unique key or primary key of the same or a different table referenced by a foreign key.
  
  
  

  Triggers

  Triggers are procedures written in PL/SQL, Java, or C that run (fire) implicitly whenever a table or view is modified or when some user actions or database system actions occur.
  Triggers supplement the standard capabilities of Oracle to provide a highly customized database management system. For example, a trigger can restrict DML operations against a table to those issued during regular business hours.
  
   
   

  Overview of Information Integration Features

  A distributed environment is a network of disparate systems that seamlessly communicate with each other. Each system in the distributed environment is called a node. The system to which a user is directly connected is called the local system. Any additional systems accessed by this user are called remote systems. A distributed environment allows applications to access and exchange data from the local and remote systems. All the data can be simultaneously accessed and modified.
  

  Distributed SQL

  A homogeneous distributed database system is a network of two or more Oracle databases that reside on one or more computers. Distributed SQL enables applications and users to simultaneously access or modify the data in several databases as easily as they access or modify a single database.
  An Oracle distributed database system can be transparent to users, making it appear as though it is a single Oracle database. Companies can use this distributed SQL feature to make all its Oracle databases look like one and thus reduce some of the complexity of the distributed system.
  Oracle uses database links to enable users on one database to access objects in a remote database. A local user can access a link to a remote database without having to be a user on the remote database.
  

  Location Transparency

  Location transparency occurs when the physical location of data is transparent to the applications and users. For example, a view that joins table data from several databases provides location transparency because the user of the view does not need to know from where the data originates.
  

  SQL and Transaction Transparency

  Oracle's provides query, update, and transaction transparency. For example, standard SQL statements like SELECT, INSERT, UPDATE, and DELETE work just as they do in a non-distributed database environment. Additionally, applications control transactions using the standard SQL statements COMMIT, SAVEPOINT, and ROLLBACK. Oracle ensures the integrity of data in a distributed transaction using the two-phase commit mechanism.
  

  Distributed Query Optimization

  Distributed query optimization reduces the amount of data transfer required between sites when a transaction retrieves data from remote tables referenced in a distributed SQL statement.
  

  Oracle Streams

  Oracle Streams enables the propagation and management of data, transactions, and events in a data stream either within a database, or from one database to another. The stream routes published information to subscribed destinations. As users' needs change, they can simply implement a new capability of Oracle Streams, without sacrificing existing capabilities.
  Oracle Streams provides a set of elements that lets users control what information is put into a stream, how the stream flows or is routed from node to node, what happens to events in the stream as they flow into each node, and how the stream terminates. By specifying the configuration of the elements acting on the stream, a user can address specific requirements, such as message queuing or data replication.
  

  Capture

  Oracle Streams implicitly and explicitly captures events and places them in the staging area. Database events, such as DML and DDL, are implicitly captured by mining the redo log files. Sophisticated subscription rules can determine what events should be captured.
  

  Staging

  The staging area is a queue that provides a service to store and manage captured events. Changes to database tables are formatted as logical change records (LCR), and stored in a staging area until subscribers consume them. LCR staging provides a holding area with security, as well as auditing and tracking of LCR data.
  

  Consumption

  Messages in a staging area are consumed by the apply engine, where changes are applied to a database or consumed by an application. A flexible apply engine allows use of a standard or custom apply function. Support for explicit dequeue lets application developers use Oracle Streams to reliably exchange messages. They can also notify applications of changes to data, by still leveraging the change capture and propagation features of Oracle Streams.
  

  Message Queuing

  Oracle Streams Advanced Queuing is built on top of the flexible Oracle Streams infrastructure. It provides a unified framework for processing events. Events generated in applications, in workflow, or implicitly captured from redo logs or database triggers can be captured in a queue. These events can be consumed in a variety of ways. They can be automatically applied with a user-defined function or database table operation, can be explicitly dequeued, or a notification can be sent to the consuming application. These events can be transformed at any stage. If the consuming application is on a different database, then the events are automatically propagated to the appropriate database. Operations on these events can be automatically audited, and the history can be retained for the user-specified duration.
  

  Data Replication

  Replication is the maintenance of database objects in two or more databases. Oracle Streams provides powerful replication features that can be used to keep multiple copies of distributed objects synchronized.
  Oracle Streams automatically determines what information is relevant and shares that information with those who need it. This active sharing of information includes capturing and managing events in the database including data changes with DML and propagating those events to other databases and applications. Data changes can be applied directly to the replica database, or can call a user-defined procedure to perform alternative work at the destination database, for example, populate a staging table used to load a data warehouse.
  Oracle Streams is an open information sharing solution, supporting heterogeneous replication between Oracle and non-Oracle systems. Using a transparent gateway, DML changes initiated at Oracle databases can be applied to non-Oracle platforms.
  Oracle Streams is fully inter-operational with materialized views, or snapshots, which can maintain updatable or read-only, point-in-time copies of data. They can contain a full copy of a table or a defined subset of the rows in the master table that satisfy a value-based selection criterion. There can be multitier materialized views as well, where one materialized view is a subset of another materialized view. Materialized views are periodically updated, or refreshed, from their associated master tables through transactionally consistent batch updates.
  

  Oracle Transparent Gateways and Generic Connectivity

  Oracle Transparent Gateways and Generic Connectivity extend Oracle distributed features to non-Oracle systems. Oracle can work with non-Oracle data sources, non-Oracle message queuing systems, and non-SQL applications, ensuring interoperability with other vendor's products and technologies.
  They translate third party SQL dialects, data dictionaries, and datatypes into Oracle formats, thus making the non-Oracle data store appear as a remote Oracle database. These technologies enable companies to seamlessly integrate the different systems and provide a consolidated view of the company as a whole.
  Oracle Transparent Gateways and Generic Connectivity can be used for synchronous access, using distributed SQL, and for asynchronous access, using Oracle Streams. Introducing a Transparent Gateway into an Oracle Streams environment enables replication of data from an Oracle database to a non-Oracle database.
  Generic Connectivity is a generic solution, while Oracle Transparent Gateways are tailored solutions, specifically coded for the non-Oracle system.