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Undo Segments
Undo SegmentsOracle Database maintains records of the actions oftransactions, collectively known as undo data. Oracle Database uses undo to dothe following:? Rollback an active transaction? Recover aterminate...
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Overview of Tablespaces
Overview of TablespacesA tablespace is a logicalstorage container for segments. Segments are database objects, such as tablesand indexes, that consume storage space. At the physical level, a tablespacestores data in one or more data files or temp files. A database must have the...
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Logical Space Management
Logical Space ManagementOracle Database must use logical space management to track and allocatethe extents in a tablespace. When a database object requires an extent, thedatabase must have a method of finding and providing it. Similarly, when anobject no longer requires an extent, the datab...
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Chained and Migrated Rows
Chained and Migrated RowsOracle Database must managerows that are too large to fit into a single block. The following situationsare possible:· The row is too large to fitinto one data block when it is first inserted.In row chaining, Oracle Database stores the data...
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checkpoint
checkpoint扫盲 什么是checkpoint checkpoint的作用 检查点分类 checkpoint相关概念术语 RBA（Redo Byte Address）, Low RBA（LRBA）, High RBA（HRBA） Buffer checkpoint Queues （BCQ） ...
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Transactions
一，Enqueued TransactionsDepending on the scenario, transactions waiting for previouslylocked resources may still be blocked after a rollback to savepoint. When atransaction is blocked by another transaction it enqueues on the blockingtransaction itself, so that the entire blocking tra...
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Oracle 常见的33个等待事件
之前整理过一篇文章： Oracle 等待事件 http://www.toadworld.com/KNOWLEDGE/KnowledgeXpertforOracle/tabid/648/TopicID/WE1/Default.aspx 13.&...
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锁 死锁 阻塞 Latch 等待 详解
锁这东西是纯概念性的东西，但是作用又非常大。 以前整理过两篇文章，今天又看了点书，觉得还不是很清楚。 就重新整理了下。 在想要不要把以前的文章删掉，这样在blog里是比较简介的，但后来又一想。 这些连接在其他的地方可能被引用了。 就决定还是保留着了，也算见证自己成长的一个过程。 ORACLE 锁机制...
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Mutex
之前也整理过一篇文章来说明Oracle Lock的，参考： 锁 死锁 阻塞 Latch 等待 详解 http://blog.csdn.net/tianlesoftware/archive/2010/08/19/5822674.aspx ...
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Overview of LOBs
Overview of LOBsThe large object (LOB) data types enable you to store and manipulate large blocks of unstructured data in binary or character format. LOBs provide efficient, random, piece-wise access to the data.Internal LOBsAn internal LOB stores data in the database itself rather...
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PL/SQL Subprograms and Packages
一Advantagesof PL/SQL SubprogramsAs explained in"Introduction to Server-Side Programming", server-side programminghas many advantages over client-side programming. PL/SQL subprograms provide the following advantages: 1.Improved performance &nb...
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Understanding Oracle OLAP Dimensions And Cubes
A reader asks:"I am new to OLAP and Oracle OLAP and I have a question. I have an Oracle 10g Database with relational tables in it. I want to create dimensions and cubes from that data. Do I nee...
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Materialized Views
Materialized Views in OracleA materialized view, or snapshot as they were previously known, is a table segment whose contents are periodically refreshed based on a query, either against a local or remote table. Using materialized views against remote tables is the simplest way to achieve re...
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Materialized Views 物化视图 －基础篇
Materialized Views 物化视图 －基础篇我相信对于了解数据仓库的朋友来说，物化视图并不陌生。但网上搜了下关于这方面的介绍相对来说还比较少，在此把自己的学习心得和大家分享。1. 数据仓库和物化视图的关系 对于典型的数据仓库来说，基于每月、每周、每天的大量数据流从一个或多...
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Partitions
Overview of PartitionsPartitioning enables you to decompose very large tables and indexes into smaller and more manageable pieces called partitions. Each partition is an independent object with its own name and optionally its own storage characteristics. 分区能将大的表或索引划分为更小的部分...
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Bitmap Indexes
Bitmap IndexesIn a bitmap index, the database stores a bitmap for each index key. In a conventional B-tree index, one index entry points to a single row. In a bitmap index, each index key stores pointers to multiple rows.Bitmap indexes are primarily designed for data warehousing or environments ...
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Oracle 索引 详解
一．索引介绍 1.1 索引的创建语法： CREATE UNIUQE | BITMAP INDEX . ON . ( |&n...
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Hash Cluster
About Hash ClustersOracle Database uses a hash function to generate a distribution of numeric values, called hash values, that are based on specific cluster key values. The key of a hash cluster, like the key of an index cluster, can be a single column or composite key (multiple column key). To fi...
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Indexex Cluster
Overview of Indexed ClustersAn indexed cluster is a table cluster that uses an index to locate data. The cluster index is a B-tree index on the cluster key. A cluster index must be created before any rows can be inserted into clustered tables.CREATE CLUSTER employees_departments_cluster &...
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Cluster Table
Overview of Table ClustersA table cluster is a group of tables that share common columns and store related data in the same blocks. When tables are clustered, a single data block can contain rows from multiple tables. For example, a block can store rows from both the employees and departments tabl...
