Friday , June 23 2017

Last Articles

Overview of Segments

Overview of Segments A segment is a set of extents that contains all the data for a logical storage structure within a table space. As explained in “Logical Space Management”, Oracle Database manages segment space automatically or manually. This section assumes the use of ASSM. You can use the DBMS_SPACE_ADMIN …

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Overview of Data Blocks

Overview of Data Blocks Oracle Database manages the logical storage space in the data files of a database in units called data blocks, also called Oracle blocks or pages. A data block is the minimum unit of database I/O. Data Blocks and Operating System Blocks At the physical level, database …

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Introduction to Logical Storage Structures

Introduction to Logical Storage Structures Oracle Database allocates logical space for all data in the database. The logical units of database space allocation are data blocks, extents, segments, and table spaces. At the finest level of granularity, Oracle Database stores data in data blocks. Locally Managed Table spaces A locally …

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Archived Redo Log Files

Archived Redo Log Files An archived redo log file is a copy of a filled member of an online redo log group. This file is not considered part of the database, but is an offline copy of an online redo log file created by the database and written to a …

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Overview of the Online Redo Log

Overview of the Online Redo Log The most crucial structure for recovery is the online redo log, which consists of two or more pre allocated files that store changes to the database as they occur. The online redo log records changes to the data files. Use of the Online Redo …

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Overview of Control Files

Overview of Control Files The database control file is a small binary file associated with only one database. Each database has one unique control file, although it may maintain identical copies of it. Use of Control Files The control file is the root file that Oracle Database uses to find …

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Overview of Data Files

Overview of Data Files At the operating system level, Oracle Database stores database data in data files. Every database must have at least one data file. Use of Data Files Oracle Database physically stores table space data in data files. Table spaces and data files are closely related, but have …

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Oracle Database Uses the Data Dictionary

How Oracle Database Uses the Data Dictionary The Oracle Database user SYS owns all base tables and user-accessible views of the data dictionary. Data in the base tables of the data dictionary is necessary for Oracle Database to function. Therefore, only Oracle Database should write or change data dictionary information. …

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Data Dictionary and Dynamic Performance Views

Data Dictionary and Dynamic Performance Views Overview of the Data Dictionary An important part of an Oracle database is its data dictionary, which is a read-only set of tables that provides administrative metadata about the database. A data dictionary contains information such as the following: ■The definitions of every schema …

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Database Instance Structures

Database Instance Structures   An Oracle database uses memory structures and processes to manage and access the database. All memory structures exist in the main memory of the computers that constitute the R DBMS. When applications connect to an Oracle database, they are connected to a database instance. Oracle Database …

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