Welcome to Oracle

by admin

When query is submitted to oracle server, various processing steps are performed to execute query. Following main steps are involved in this process.

1- Query Parsing

2- Optimizer determines most efficient way to execute query and generates an execution plan.

3- Finally SQL engine executes query.

In 1^st step, SQL server checks syntax of query and outputs error if found.

After parsing of query, optimizer generates execution plan. Execution plan produced by optimizer depends on two main possible goals Continue reading SQL Processing

Oracle Database Architecture

by admin

Oracle Database Architecture consists of following three main structures

1- Storage Structure

2- Memory Structure

3- Process Structure

Two of these constitute in primary storage and one in secondary storage.

When a database is created, database files are installed on secondary storage. These files include Control files, Data files, online redo log files, parameter file and password file. All these files formulate “Storage Structure”. Continue reading Oracle Database Architecture

by admin

Oracle Corporation is one of the leading IT companies at the moment. Oracle Corporation offers multiple software solution for almost all business areas. List of Products owned by oracle provide us a glint.
List of oracle products
This website will focus on Oracle Database. Oracle RDBMS is undoubtedly the most popular and widely used database. Oracle Database 10g and Oracle Database 11g are the hottest versions at the moment. exploreoracle.com will make an effort to cover following core and basic topics

Database Architecture
Backup and Recovery ( OS level and RMAN)
Performance and tunning
Flash back Features
Auditing & Scheduling
External tables and SQL Loader

Tasks will be performed using Oracle EM as well as CLI .

Jul

Redo Log Buffer & Log writer process (LGWR)

by admin

Oracle database keeps record of changes made to data. Every time user performs a DML, DDL or DCL operation, its redo entries are also created. These redo entries contain commands to rebuild or redo the changes. These entries are stored in Redo Log buffer. Log writer process (LGWR) writes these redo entries to redo log files. Redo log buffer works in circular fashion. It means that it overwrites old entries. Continue reading Redo Log Buffer & Log writer process (LGWR)

Posted in DataBase Architecture | No Comments

Apr

Keep Buffer Pool and Recycle Buffer Pool

by admin

Data required by oracle user process is loaded into buffer cache, if it is not already present in cache. Proper memory tuning is required to avoid repeated disk access for the same data. This means that there should be enough space in buffer cache to hold required data for long time. If same data is required in very short intervals then such data should be permanently pinned into memory. Oracle allows us to use multiple buffers. Using multiple buffers we can control that how long objects should be kept in memory.

Continue reading Keep Buffer Pool and Recycle Buffer Pool

Posted in DataBase Architecture, Oracle Database 10g | No Comments

Mar

Database Buffer Cache

by admin

Database Buffer cache is one of the most important components of System Global Area (SGA). Database Buffer Cache is the place where data blocks are copied from datafiles to perform SQL operations. Buffer Cache is shared memory structure and it is concurrently accessed by all server processes.

Working of Database buffer Cache

Buffer Cache is organized into two lists

Write List

Write list contains dirty buffers. These are the data blocks which contain modified data and needed to be written to datafiles.

Continue reading Database Buffer Cache

Posted in DataBase Architecture, Oracle Database 10g | No Comments