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Archive for the ‘Oracle RDBMS’ Category
  1. 1.什么是控制文件?
    控制文件是ORACLE数据库用来记录数据库物理结构信息的一个二进制文件.控制文件在数据库创建的同时被创建,
    默认情况下ORACLE会创建一个控制文件镜像(最多可以有8个镜像)。ORACLE数据库MOUNT的时候会读取控制文件,
    所以如果没有控制文件,数据库就不能被挂载(MOUNT)和打开(OPEN)。控制文件的内容由ORACLE 数据库自己管理,
    在数据库运行的时候(OPEN STATE),数据库会不断更新控制文件的内容。
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    Popularity: 34% [?]

  2. 查找无效对象
    你可以根据这个查询结果来判断使用下面的哪种方法来编译你数据库礼貌的无效对象.

    COLUMN object_name FORMAT A30 
    SELECT owner, 
    object_type, 
    object_name, 
    STATUS 
    FROM dba_objects 
    WHERE STATUS = 'INVALID' 
    ORDER BY owner, object_type, object_name;

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    Popularity: 22% [?]

  3. 概述
    数据文件是用来存储数据库中所有逻辑结数据的物理文件,它是一个操作系统文件.我们可以用ls(UNIX/LINUX操作系统命令)在操作系统级查看到这些文件.我们在创建表空间的时候需要显式的制定数据文件.
    ORACLE在创建数据文件的时候会给每个数据文件分配两个相关的文件编号, 绝对文件号(absolute file number)和相对文件号(relative file number).
    绝对文件号:
    在整个数据库中唯一标识数据文件.
    相对文件号:
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    Popularity: 25% [?]

  4. ORA-01792 maximum number of columns in a table or view is 1000
    Cause: An attempt was made to create a table or view with more than 1000 columns, or to add more columns to a table or view which pushes it over the maximum allowable limit of 1000. Note that unused columns in the table are counted toward the 1000 column limit.
    Action: If the error is a result of a CREATE command, then reduce the number of columns in the command and resubmit. If the error is a result of an ALTER TABLE command, then there are two options:
    * If the table contained unused columns, remove them by executing ALTER TABLE DROP UNUSED COLUMNS before adding new columns.
    * Reduce the number of columns in the command and resubmit.
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    Popularity: 28% [?]

  5. 今天用户运行查询语句的时候遇到了Ora-01775错误,查看了一下帮助得到如下解释:

    ORA-01775 looping chain of synonyms
    Cause: Through a series of CREATE synonym statements, a synonym was defined that referred to itself. For example, the following definitions are circular:
    CREATE SYNONYM s1 for s2
    CREATE SYNONYM s2 for s3
    CREATE SYNONYM s3 for s1
    Action: Change one synonym definition so that it applies to a base table or view and retry the operation.
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    Popularity: 28% [?]

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