Oracle DBA Tutorial
Database or simply DB is an organized and structured collection of information which can be to efficiently retrieved, updated and analyzed. A simple VB code, C, excel or notepad cannot manage large number of users and files. Also easy extraction, backup and restoration of data is not possible with this approach. To counter this limitation Oracle has come up with Oracle database or Oracle RDBMS.
It is the relational database management system. The main objective of this is to store, manage and retrieve information efficiently to deliver high performance. It is also termed as RDBMS or simply Oracle.
Oracle consists of various software mechanisms to achieve maximized data concurrency, high performance for maximum productivity for multi users in database environment.
In Oracle, there are three basic categories of physical files used to store information. These are –
- Data files- It contains the data required to start the database engine.
- Control files- It is the storehouse of metadata of the database used by the Oracle engine.
- Redo log files- These files are used to store the changes made to the database.
- Parameter Files
To Learn Oracle DBA, it is required to understand the basic terminologies used in it.
- Instance – It is defined as the background processes and memory structure used to retrieve data from a database.
- Process- Also termed as task or job, is a running instance. There are two types of processes in Oracle database system namely, Oracle processes and User processes. There is no need to use any operating system command to interact with the database.
- Buffer Cache – It is SGA component which acts like a buffer to store the data being customized or queried. It stores the most recently or frequently used data in memory which improves the performance. All the user processes that are connected to the database share an access to it.
- Shared pool- It captures information to be shared with users. For example: stored procedures, SQL statements etc can be cached for reusability and fast access.
- Redo Log Buffer- It maintains a log of changes that are made in the database. The redo log files run in circular motion and get overwritten. So, to maintain the recoverability of the database for longer duration, they are archived into archive logs. Therefore, redo log helps to recover an instance when there is a system failure. This improves the performance and functioning of the database system.
- Large pool- It is the optional area that offer memory allocations for large processes, like recovery operations and Oracle backup.
- Locks- For controlling the simultaneous access to data resources, locks are used.
The database consists of logical and physical structures. Because these structures are separate, the management of physical storage of data does not affect the access to logical structures.
Above mentioned information is required to get the basic understanding of the database. We have tried to cover all important parameters and terms used in Oracle.