Oracle Architecture

Hi guys, in this blog I am going to explain you about Oracle Architecture.

Oracle Architecture-

The relational database management system (RDBMS) known as Oracle Database was developed and commercialized by Oracle Corporation. One of the most widely used RDBMSs available, it is used to store and retrieve data for a variety of purposes. The Oracle Database is widely recognized for its performance, scalability, and dependability. It also works with a variety of development frameworks and programming languages. It encompasses high availability, disaster recovery, security, and advanced analytics in addition to data warehousing and online transaction processing.

The database server and client connections operate independently in Oracle Database's client-server architecture. Data access and manipulation are accomplished through communication between client connections and the server process, which controls resources and data. Oracle Database supports a number of programming interfaces, including Java, SQL, and PL/SQL, which is Oracle's own procedural language. Additionally, it comes with database administration and management tools including SQL Plus and Oracle Enterprise Manager.

 

The oracle database architecture consists of:  

• Memory structure (Instances) 
• Processes 
• Database system

Oracle Instances-

The instance is a collection of two things: 

 

SGA- 

For System Global Area, it stands. It is a region of shared memory. SGA memory is the RAM that is allocated when a database instance first launches. Memory allocation will occur in addition to one or more background processes. Through its several subcomponents, each of which is devoted to a particular function, SGA is used to store data and manage information about a single database instance. Different parts are:

Shared pool-

 

Shared memory structures, including shared SQL and PL/SQL regions, are found in the Shared Pool, a section of the SGA. It holds the parsed representations of PL/SQL programmed units, execution plans, and SQL statements. By enabling the effective reuse of frequently performed statements, reparsing becomes less necessary, resulting in improved speed. 

 

Database buffer cache-

A section of the SGA called the Buffer Cache is used to store copies of data blocks that are read from datafiles. It lowers the amount of disc I/O needed to access the data by caching frequently requested data blocks. This can speed up data retrieval and cut down on disc I/O time, both of which can enhance performance.

 

Redo log Buffer-

The redo log, which is made up of two or more reallocated files that record all database changes as they happen, is the most important structure for recovery operations. An associated redo log is attached to each Oracle database instance in order to safeguard the database in the event of an instance failure.

 

There are two types of processes-

 

User process-

 

It is also known as the client process the user actually connects to the instance with the help of user processes.

the user process is stabilized when the user sends a connection request to the oracle server. 

 

Server process-

 

The server Process connects the user to the database and performs the activities on the client’s behalf as executing SQL statements or retrieving data from the database. 

 

 

Background processes-

 

Oracle background processes are a group of related processes. These processes are in charge of memory management, I/O operations, and other upkeep duties. The following are some crucial preparatory steps that must be completed:

 

System Monitor Process (SMON)-

 

These processes are responsible for performing system-level recovery and maintenance activities.

 

 

Process Monitor Process (PMON)-

 

The task of these processes is to monitor other background processes. 

 

 

 

Database Writer Process (DBWR)-

 

This process performs the task of writing data blocks from the Database Buffer Cache (present in SGA) to physical data files (Present in the Database system). 

 

 

Log Writer Process (LGWR)-

 

This process writes the Redo blocks from Redo Log Buffer (present in SGA) to Redo Log Files (present in the Database system). 

 

Checkpoint (CKPT)-

 

This process maintains data files and control files with the most recent checkpoint information. 

Archiver Recover-

An "Archiver Recover" in Oracle has no particular function or significance. Although the technique of restoring a database using archived log files is known as "archiver recovery," there is no official word or position in Oracle named "Archiver Recover."

 

Database System-

 

The database system is suited to the storage system of a computer. The Database system is simply the storage of files. There are three categories of files that are situated in the database system and those are: - 

 

Data files-

 

These files hold the actual data in the database. 

 

Redo log files-

 

These files are used to hold the changes made in the database. Redo log files can be utilized during the database recovery process to retrieve the original information. 

 

 

Control files-

 

It is a binary file that holds database status-related information like Database Name, Data File, and Redo Log file Names, File Locations, and Log Sequence Number.  

 

There are other categories of files that contribute to database management.  

 

Parameter file-

 

This file contains the parameters which define the way the database is expected to start up. 

 

Password file-

This file holds the user passwords and thus maintains the security of databases. 

Archived log file-

In Oracle 19c, archived log files are copies of redo log files that have been preserved and stored for backup and recovery purposes. These files track database changes and are necessary for restoring the database to a given point in time, such as during a recovery operation or when implementing data backups.