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10g默认没有创建role : plustrace , 非sys用户在使用set autot语句时出错set">test@ora10g>set autot traceonlySP2-0618: 无法找到会话标识符。启用检查 PLUSTRACE 角色SP2-0611: 启用 STATISTICS 报告时出错解决:%ohome%sqlplusadmin>sqlplus / as sysdba @plustrcegrant plustrace to test;test用户重连后即可正常使用。[@more@]

Specifies the type of database optimizer statistics to generate when theexported data is imported. Options are ESTIMATE,COMPUTE, and NONE.In some cases, Export will place the precalculated statistics in the export fileas well as the ANALYZE statements to regenerate the statistics.However, the precalculated optimizer statistics will not be used at export timeif a table has columns with system-generated names.The precalculated optimizer statistics are flagged as questionable at exporttime if:■ Th

Monitor transaction and undo information with V$TRANSACTION and V$ROLLSTAT. For automatic undo management, the information in V$ROLLSTAT reflects the behaviors of the automatic undo management undo segments.The V$UNDOSTAT view displays a histogram of statistical data to show how well the system is working. You can see statistics such as undo consumption rate, transaction concurrency, and lengths of queries run in the instance. Using this view, you can better estimate the amount of undo space req

The TABLESPACES parameter specifies that all tables in the tablespace beexported to the Export dump file. This includes all tables contained in the listof tablespaces and all tables that have a partition located in the list oftablespaces. Indexes are exported with their tables, regardless of where theindex is stored. You must have the EXP_FULL_DATABASE role to use TABLESPACES toexport all tables in the tablespace.When TABLESPACES is used in conjunction withTRANSPORT_TABLESPACE=y,you can specify

Oracle Database 10g automatically tunes a parameter called the undo retentionperiod.The undo retention period indicates the amount of time that must pass before oldundo information—that is, undo information for committed transactions—can beoverwritten. The database collects usage statistics and tunes the undo retentionperiod based on these statistics and on undo tablespace size. Provided that automaticundo management is enabled, the database automatically tunes the undo retentionperiod as foll

In automatic undo management mode, the system controls exclusively theassignment of transactions to undo segments, and controls space allocation for undo segments. An ill-behaved transaction can potentially consume much of the undo space, thus paralyzing the entire system. The Resource Manager directive UNDO_POOL is a more explicit way to control large transactions. This lets database administrators groupusers into consumer groups, with each group assigned a maximum undo space limit. When the to

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Undo mode provides a more flexible way to migrate from manual undo management to automatic undo management. A database system can run in either manual undo management mode or automatic undo management mode. In manual undo management mode, undo space is managed through rollback segments. In automatic undo management mode, undo space is managed in undo tablespaces. To use automatic undo management mode, the database administrator needs only to create an undo tablespace for each instance and set th

Oracle maintains information to nullify changes made to the database. Such information consists of records of the actions of transactions, collectively known as undo. Oracle uses the undo to do the following:■ Rollback an active transaction■ Recover a terminated transaction■ Provide read consistency■ Recovery from logical corruptionsAutomatic undo management eliminates the complexities of managing rollback segment space and lets you exert control over how long undo is retained before being o

Oracle allocates segments for a temporary table when the first INSERT into that table is issued. (This can be an internal insert operation issued by CREATE TABLE AS SELECT.) The first INSERT into a temporary table allocates the segments for the table and its indexes, creates the root page for the indexes, and allocates any LOB segments. Segments for a temporary table are allocated in a temporary tablespace of the user who created the temporary table. Oracle drops segments for a transaction-speci

Oracle allocates temporary segments as needed during a user session in one of the temporary tablespaces of the user issuing the statement. Specify these tablespaces with a CREATE USER or an ALTER USER statement using the TEMPORARY TABLESPACE clause. If no temporary tablespace is defined for the user, then the default temporary tablespace is the SYSTEM tablespace. The default storage characteristics of the containing tablespace determine those of the extents of the temporary segment. Oracle drops

The following statements sometimes require the use of a temporary segment: ■ CREATE INDEX ■ SELECT ... ORDER BY ■ SELECT DISTINCT ... ■ SELECT ... GROUP BY ■ SELECT . . . UNION ■ SELECT ... INTERSECT ■ SELECT ... MINUS Some unindexed joins and correlated subqueries can require use of a temporary segment. For example, if a query contains a DISTINCT clause, a GROUP BY, and an ORDER BY, Oracle can require as many as two temporary segments. 1. 以上7种情况可能用到临时段2. Oracle一条SQL最多

When processing queries, Oracle often requires temporary workspace for intermediate stages of SQL statement parsing and execution. Oracle automatically allocates this disk space called a temporary segment. Typically, Oracle requires a temporary segment as a database area for sorting. Oracle does not create a segment if the sorting operation can be done in memory or if Oracle finds some other way to perform the operation using indexes. 1. 临时段经常用做SQL解析和执行2. 典型的情况是临时段用做

今天邂逅ORA-12638错误 , 身份证明检索失败.C:>oerr ora 12638ORA-12638: Credential retrieval failedCause: The authentication service failed to retrieve the credentials of a user.Action: Enable tracing to determine the exact error.credential外交使节所递的国书, 信任状不明白 , 百度一把 , 原因是由于Oracle不能应用OS认证而导致凭证检索失败,处理方法:修改%oracle_home%/network/admin下的sqlnet.ora，将SQLNET.AUTHENTICATION_SERVICES=(NTS)屏蔽即ok但是为什么会有这个错误 , 屏蔽了这个参数对后面有什么影响还得继续

Every nonpartitioned index in an Oracle database has a single index segment to hold all of its data. For a partitioned index, every partition has a single index segment to hold its data. Oracle creates the index segment for an index or an index partition when you issue the CREATE INDEX statement. In this statement, you can specify storage parameters for the extents of the index segment and a tablespace in which to create the index segment. (The segments of a table and an index associated with it

PRE_PAGE_SGA determines whether Oracle reads the entire SGA into memory at instance startup. Operating system page table entries are then prebuilt for each page of the SGA. This setting can increase the amount of time necessary for instance startup, but it is likely to decrease the amount of time necessary for Oracle to reach its full performance capacity after startup.[@more@]

This parameter allows you to select a subset of rows from a set of tables when doinga table mode export. The value of the query parameter is a string that contains aWHERE clause for a SQL SELECT statement that will be applied to all tables (or tablepartitions) listed in the TABLE parameter.If a table is missing the columns specified in the QUERY clause, an error messagewill be produced, and no rows will be exported for the offending table.Restrictionsn The parameter QUERY cannot be specified for

A single data segment in an Oracle database holds all of the data for one of the following:■ A table that is not partitioned or clustered■ A partition of a partitioned table■ A cluster of tablesOracle creates this data segment when you create the table or cluster with the CREATE statement.1. 三者的并集是全集啊2. 当使用create语句创建表时 , Oracle创建数据段[@more@]

A segment is a set of extents that contains all the data for a specific logical storage structure within a tablespace. For example, for each table, Oracle allocates one or more extents to form that table’s data segment, and for each index, Oracle allocates one or more extents to form its index segment.1. 包含某指定的逻辑存储结构的所有数据3., 构成, (使

1、待机”电源管理模式 待机模式主要用于节电，该功能使你可不需重新启动计算机就可返回工作状态。待机模式可关闭监视器和硬盘、风扇之类设备，使整个系统处于低能耗状态。在你重新使用计算机时，它会迅速退出待机模式，而且桌面（包括打开的文档和程序）精确恢复到进入等待时的状态。 如要解除等待状态并重新使用计算机，可移动一下鼠标或按键盘上的任意键，或快速按一下计算机上的电源按钮即可。 请注意！与下面所述的“休眠模式”不同，待机模式不在硬盘上存储未保存的信息，这些信息仅仅只存储在计算机内存中。如果期间突然断电，这些