Oracle Products and Database Architecture Explained
Oracle Products
Oracle Databases
The Oracle database is designed for Enterprise Grid Computing.
Oracle Application Server
Certified for Java 2 Platform Enterprise Edition (J2EE), Oracle provides the tools to develop and deploy Web-based applications.
Oracle Applications
Oracle E-Business Suite is a complete set of business applications.
Oracle Collaboration Suite
Oracle Collaboration Suite is a single integrated system for all data communications.
Global Grid Forum (GGF)
The Global Grid Forum (GGF) is an organization that develops standards for Grid Computing.
Automatic Storage Management (ASM)
Automatic Storage Management distributes data from databases for all records, creates and maintains a storage grid, and delivers performance and input/output efficiency.
Oracle Real Application Clusters (RAC)
Oracle RAC allows you to run and scale all application workloads in a cluster of servers.
Integrated Clusterware
Includes functionality for cluster connectivity, messaging and locking, cluster control, and recovery.
Automatic Management of Workloads
You can define rules to automatically allocate processing resources to each service during operations.
Notification of Automatic Events to the Middle Layer
When you change a cluster configuration, the middle layer can adapt immediately to the failover operation, allowing end users to continue working during a failover.
Oracle Streams
Oracle Streams provides a unified framework for sharing information. It can keep two or more copies of a data source synchronized when applying updates at any of the sites.
Enterprise Manager Grid Control
Enterprise Manager Grid Control manages the operations of the grid, including managing the entire software stack, user provisioning, cloning of databases, and patch management.
Oracle Database Architecture
Key to Information Management
The Oracle server is key to information management. An Oracle server reliably manages a large amount of data in a multi-user environment, allowing many users to simultaneously access the same data.
Database Structure
Each running Oracle database is associated with an Oracle instance. When a database is started on a database server, the Oracle software allocates a shared memory area called the System Global Area (SGA) and starts several background processes. This combination of SGA and Oracle processes is called the Oracle instance.
Basic Memory Structures
The basic memory structures associated with an Oracle instance include:
- System Global Area (SGA): Shared by all server processes and background processes.
- Program Global Area (PGA): Private to each server process in the background. There is a PGA for each process.
Common Background Processes
The most common background processes are:
- System Monitor (SMON): Performs failover when the instance starts after a crash.
- Process Monitor (PMON): Performs cleaning processes when a user process fails.
- Checkpoint (CKPT): Updates all data files and control files of the database to indicate the most recent checkpoint.
Buffer Cache States
The buffer cache buffers can have one of the following four states:
- Assigned: Prevents multiple sessions from writing to the same block simultaneously. Other sessions wait to enter the block.
- Clean: The buffer is not assigned and is now a candidate for immediate obsolescence if the current content (data block) is not re-referenced. The content is synchronized with the contents of blocks stored on disk, or the buffer contains a snapshot of Consistent Read (CR) in a block.
- Free or Not Used: The buffer is empty because the instance has just started. This state is very similar to the clean state, except the buffer has not been used.
- Dirty: The buffer is allocated, but the content (data block) has changed and should be emptied on the disk with DBWn before it becomes stale.