Contributors: Drew Adams, David Austin, Vladimir Barriere, Hermann Baer, David Brower, Jonathan. Creighton, Bjørn Engsig, Steve Fogel, Bill Habeck, Bill. Architecture Diagram. IIIIIIIIIIIIIII. MMNL. RCBG. PMON menu enou. 2". VKRM. ( Virtual Scheduler for. Resource Manager) am. SMON. MMAN. (Memory Manager ). Oracle Database Architecture. Overview of Application Architecture. Client/ Server Architecture. Multitier Architecture: Service-Oriented Architecture.
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preferably some knowledge of Oracle an introduction to the architecture of Oracle . The following •The Oracle Server itself, which is were the database resides. The Oracle architecture includes a number of primary components, which are Oracle server: There are several files, processes, and memory structures. architecture (Section ) and the logical and physical database structures The Oracle DBMS server is based on a so-called Multi-Server Architecture.
The reduction in the number of pre-built objects results in reduced storage space and significantly less processing overhead. The database transparently sends OLTP queries such as primary key lookups to the buffer cache, and analytic and reporting queries to the IM column store. Thus, dual memory formats provide the best of both worlds.
The following figure shows a sample IM column store. The sh. The SGA stores the data in columnar format in the IM column store, and in row format in the database buffer cache. The columnar format does not affect the format of data stored in data files or in the buffer cache, nor does it affect undo, online redo logging, and so on.
The database processes DML modifications in the same way regardless of whether the IM column store is in use: by updating the buffer cache, online redo log, undo tablespace, and so on. However, the database uses an internal mechanism to track changes and ensure that the IM column store is consistent with the rest of the database. For example, if the sales table resides in the IM column store, and if a row in sales is updated, then the database automatically ensures the copy of the sales table in the IM column store is kept transactionally consistent.
A query that accesses the IM column store always returns the same results for a query that accesses the buffer cache. Worker processes Wnnn populate the data in the IM column store. Each worker process operates on a subset of database blocks from the object. Population is a streaming mechanism, simultaneously compressing the data and converting it into columnar format.
Set this parameter to an appropriate value for your environment. More worker processes result in faster population, but they use more CPU resources. Fewer worker processes result in slower population, which reduces CPU overhead. This reconstruction is necessary because the IM column store resides only in memory.
When the INMEMORY attribute is set for an object, the database may choose not to materialize all columns when the database determines that the memory is better used elsewhere. Also, the IM column store may populate a subset of columns from a table.
To determine whether data from the sh. Oracle instance: An Oracle Instance consists of two different sets of components: The second component set includes the memory structures that comprise the Oracle instance.
An Oracle Instance provides access to one and only one Oracle database. Oracle database: An Oracle database consists of files.
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Sometimes these are referred to as operating system files, but they are actually database files that store the database information that a firm or organization needs in order to operate.
The redo log files are used to recover the database in the event of application program failures, instance failures and other minor failures. The archived redo log files are used to recover the database if a disk fails. Other files not shown in the figure include: User and server processes: The processes shown in the figure are called user and server processes. These processes are used to manage the execution of SQL statements.
A Shared Server Process can share memory and variable processing for multiple user processes. A Dedicated Server Process manages memory and variables for a single user process. This connection enables users to execute SQL statements. The User Process executes on the client computer.
The Server Process executes on the server computer, and actually executes SQL statements submitted by the system user.
This is called a Dedicated Server connection. When a user connects to an Oracle server, this is termed a session.
The User Global Area is session memory and these memory structures are described later in this document. The session starts when the Oracle server validates the user for connection.
The session ends when the user logs out disconnects or if the connection terminates abnormally network failure or client computer failure. A user can typically have more than one concurrent session, e.
The limit of concurrent session connections is controlled by the DBA. If a system users attempts to connect and the Oracle Server is not running, the system user receives the Oracle Not Available error message. Physical Structure — Database Files As was noted above, an Oracle database consists of physical files. The database itself has: Datafiles — these contain the organization's actual data. Redo log files — these contain a chronological record of changes made to the database, and enable recovery when failures occur.
Control files — these are used to synchronize all database activities and are covered in more detail in a later module. Other key files as noted above include: Parameter file — there are two types of parameter files.
It contains parameters that specify how the database instance is to start up. These values are stored in the init. Three basic options for memory management are as follows: Automatic memory management: Automatic shared memory management: Manual memory management: If you create a database with Database Configuration Assistant DBCA and choose the basic installation option, then automatic memory management is the default.
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The memory structures include three areas of memory: The SGA has the following mandatory memory structures: This meant that if modifications to memory management were required, the database had to be shutdown, modifications were made to the init. Oracle 11g uses a Dynamic SGA. Memory configurations for the system global area can be made without shutting down the database instance. Several initialization parameters are set that affect the amount of random access memory dedicated to the SGA of an Oracle Instance.
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These are: This optional parameter is used to tune the amount memory allocated to the Database Buffer Cache in standard database blocks. Block sizes vary among operating systems.
The default is 16 MB. If the operating system is based on a 64 bit configuration, then the default size is 64 MB.
This is an optional memory object — the size of the Large Pool defaults to zero.Shared servers place all completed requests into a dispatcher's response queue. In Server Manager, the command used for starting any database is the startup command. The Shared Pool — The contents of this memory area are shared by multiple users and hence the name shared pool.
This activity should not require much effort from the DBA, as Oracle will handle the recovery of the database instance itself without much intervention. From the prior discussion of the shared pool, the DBA should know that the database already stores parse trees for recently executed SQL statements in a shared area called the library cache.
The following figure shows a sample IM column store. The complete syntax of its usage is displayed below: When archivelog is used, Oracle archives the redo logs generated. This resource stores passwords for users who have administrative privileges over the Oracle database. The Keep cache is used to hold such.