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随着对Oracle数据库的不断学习和使用，对Oracle基本概念越来越熟悉了。
“锲而不舍，金石可镂！” 学习是一项终身的事业！
| 概念 | 中文 | 描述 |
| background process | 后台进程 | A process that consolidates functions that would otherwise be handled by multiple Oracle programs running for each client process. The background processes asynchronously perform I/O and monitor other Oracle processes. See also database instance; Oracle process. |
| backup | 备份 | A copy of data. A backup can include crucial parts of the database such as data files, the server parameter file, and control file. |
| backup piece | 最小备份单元 | The smallest unit of a backup set. |
| backup set | 备份集 | A proprietary RMAN backup format that contains data from one or more data files, archived redo log files, or control files or server parameter file. |
| big table cache | Big Table缓存 | An optional, integrated portion of the database buffer cache that uses a temperature-based, object-level replacement algorithm instead of the traditional LRU-based, block-level replacement algorithm. |
| bigfile tablespace | Bigfile表空间 | A tablespace that contains one very large data file or temp file. |
| bind variable | 绑定变量 | A placeholder in a SQL statement that must be replaced with a valid value or value address for the statement to execute successfully. By using bind variables, you can write a SQL statement that accepts inputs or parameters at run time. The following example shows a query that uses v_empid as a bind variable: SELECT * FROM employees WHERE employee_id = :v_empid; |
| bitmap index | 位图索引 | A database index in which the database stores a bitmap for each index key instead of a list of rowids. |
| bitmap join index | 位图连接索引 | A bitmap index for the join of two or more tables. |
| bitmap merge | 位图合并 | An operation that merges bitmaps retrieved from bitmap index scans. For example, if the gender and DOB columns have bitmap indexes, then the database may use a bitmap merge if the query predicate is WHERE gender='F' AND DOB > 1966. |
| block corruption | 数据块损坏 | A data block that is not in a recognized Oracle format, or whose contents are not internally consistent. |
| block header | 数据块头部 | A part of a data block that includes information about the type of block, the address of the block, and sometimes transaction information. |
| block overhead | 数据块开销 | Space in a data block that stores metadata required for managing the block. The overhead includes the block header, table directory, and row directory. |
| branch block | 分支数据块 | In a B-tree index, a block that the database uses for searching. The leaf blocks store the index entries. The upper-level branch blocks of a B-tree index contain index data that points to lower-level index blocks. |
| buffer | 缓存 | A main memory address in the database buffer cache. A buffer caches currently and recently used data blocks read from disk. When a new block is needed, the database can replace an old data block with a new one. |
| buffer cache hit ratio | 缓存命中率 | The measure of how often the database found a requested block in the buffer cache without needing to read it from disk. |
| buffer pool | 缓存池 | A collection of buffers in the SGA. |
| business intelligence | 商务智能 | The analysis of an organization's information as an aid to making business decisions. |
| byte semantics | 字节语义 | Treatment of strings as a sequence of bytes. Offsets into strings and string lengths are expressed in bytes. |
| cache recovery | 缓存恢复 | The automatic phase of instance recovery where Oracle Database applies all committed and uncommitted changes in the online redo log files to the affected data blocks. |
| cardinality | 基数（唯一值的数量与数据表行数的比值） | The ratio of distinct values to the number of table rows. A column with only two distinct values in a million-row table would have low cardinality. |
| Cartesian join | 笛卡尔连接 | A join in which one or more of the tables does not have any join conditions to any other tables in the statement. The optimizer joins every row from one data source with every row from the other data source, creating the Cartesian product of the two sets. |
| CDB (Container Database) | CDB (容器数据库) | An Oracle Database installation that contains at least one PDB. A PDB appears to an Oracle Net client as a traditional Oracle database. Every Oracle database is either a CDB or a non-CDB. |
| CDB administrator | CDB管理员 | A database administrator who manages a CDB. A PDB administrator manages individual PDBs within the CDB. |
| character encoding | 字符编码 | A code that pairs each character from a given repertoire with a code unit to facilitate data storage. |
| character semantics | 字符语义 | Treatment of strings as a sequence of characters. Offsets into strings and string lengths are expressed in characters (character codes). |
| character set | 字符集 | An encoding scheme used to display characters on your computer screen. |
| check constraint | 检查约束 | A constraint on a column or set of columns that requires a specified condition to be true or unknown for every row. |
| checkpoint | 检查点 | 1. A data structure that marks the checkpoint position, which is the SCN in the redo thread where instance recovery must begin. Checkpoints are recorded in the control file and each data file header, and are a crucial element of recovery. 2. The writing of dirty data blocks in the database buffer cache to disk. The database writer (DBW) process writes blocks to disk to synchronize the buffer cache with the data files. |
| checkpoint process (CKPT) | 检查点进程 | The background process that updates the control file and data file headers with checkpoint information and signals DBW to write blocks to disk. |
| child cursor | 子游标 | The cursor containing the plan, compilation environment, and other information for a statement whose text is stored in a parent cursor. The parent cursor is number 0, the first child is number 1, and so on. Child cursors reference exactly the same SQL text as the parent cursor, but are different. For example, two statements with the text SELECT * FROM mytable use different cursors when they reference tables named mytable in different schemas. |
| circular reuse record | 循环复用记录 | A type of control file record that contains noncritical information that is eligible to be overwritten if needed. When all available record slots are full, the database either expands the control file to make room for a new record or overwrites the oldest record. |
| client | 客户端程序 | In client/server architecture, the front-end database application that interacts with a user. The client portion has no data access responsibilities. |
| client character set | 客户端字符集 | The character set for data entered or displayed by a client application. The character set for the client and database can be different. |
| client process | 客户端进程 | A process that executes the application or Oracle tool code. When users run client applications such as SQL*Plus, the operating system creates client processes to run the applications. See also Oracle process. |
| client/server architecture | 客户端/服务器架构 | Software architecture based on a separation of processing between two CPUs, one acting as the client in the transaction, requesting and receiving services, and the other as the server that provides services in a transaction. |
| cluster file system | 集群文件系统 | A distributed file system that is a cluster of servers that collaborate to provide high performance service to their clients. |
| cluster index | 集群索引 | A B-tree index on the cluster key. |
| cluster key | 集群键 | In a table cluster, the column or columns that the clustered tables have in common. For example, the employees and departments tables share the department_id column. Specify the cluster key when creating the table cluster and when creating every table added to the table cluster. |
| cold buffer | 冷缓存 | A buffer in the database buffer cache that has not been recently used. |
| column | 列 | Vertical space in a table that represents a domain of data. A table definition includes a table name and set of columns. Each column has a name and data type. |
| columnar format | 列格式 | The column-based format for objects that reside in the In-Memory Column Store. The columnar format contrasts with the row format that the database uses to store objects in the database buffer cache and in data files. |