Friday , June 23 2017

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Server Result Cache

Server Result Cache

Server Result Cache Unlike the buffer pools, the server result cache holds result sets and not data blocks. The server result cache contains the SQL query result cache and PL/SQL function result cache, which share the same infrastructure. A client result cache differs from the server result cache. A client …

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Overview of the System Global Area

System Global Area

Overview of the System Global Area The SGA is a read/write memory area that, along with the Oracle background processes, makes up a database instance. All server processes that execute on behalf of users can read information in the instance SGA. Several processes write to the SGA during database operation. …

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ADR Structure

ADR Structure The ADR base is the ADR root directory. The ADR base can contain multiple ADR homes, where each ADR home is the root directory for all diagnostic data—traces, dumps, the alert log, and so on—for an instance of an Oracle product or component. Alert Log Each database has …

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Overview of Diagnostic Files

Overview of Diagnostic Files Oracle Database includes a fault diagnosability infrastructure for preventing, detecting, diagnosing, and resolving database problems. Problems include critical errors such as code bugs, metadata corruption, and customer data corruption. The goals of the advanced fault diagnosability infrastructure are the following: Detecting problems proactively Limiting damage and …

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Overview of Oracle Parameter Files

Overview of Parameter Files To start a database instance, Oracle Database must read either a server parameter file, which is recommended, or a text initialization parameter file, which is a legacy implementation. These files contain a list of configuration parameters. To create a database manually, you must start an instance …

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Oracle System Identifier (SID)

Oracle System Identifier (SID) The System identifier (SID) is a unique name for an Oracle database instance on a specific host. On UNIX and Linux, Oracle Database uses the SID and Oracle home values to create a key to shared memory. Also, the SID is used by default to locate …

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Temporary Tablespaces

Temporary Table spaces A temporary table space contains transient data that persists only for the duration of a session. No permanent schema objects can reside in a temporary table space. The database stores temporary table space data in temp files. Temporary table spaces can improve the concurrency of multiple sort …

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Automatic Undo Retention

Automatic Undo Retention The undo retention period is the minimum amount of time that Oracle Database attempts to retain old undo data before overwriting it. Undo retention is important because long-running queries may require older block images to supply read consistency. Also, some Oracle Flashback features can depend on undo …

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Undo Table spaces

Undo Table spaces An undo table space is a locally managed table space reserved for system-managed undo data. Like other permanent table spaces, undo table spaces contain data files. Undo blocks in these files are grouped in extents. Automatic Undo Management Mode Undo table spaces require the database to be …

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Overview of Table spaces

Overview of Table spaces A table space is a logical storage container for segments. Segments are database objects, such as tables and indexes, that consume storage space. At the physical level, a table space stores data in one or more data files or temp files. A database must have the …

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