Oraclecorruptblock（坏块）详解(3)

datadictionary 是在创建时通过$ORACLE_HOME/dbs/sql.bsq脚本创建的，并且这些核心的表，索引和clusters 不能被drop 和recreate。 他们在db 启动时使用。

2) Views createdon the fixed data structures (V$ views).

3)SYSTEM rollback segment created after the databasecreation. If the corruption is in this segment, then the most recentbackup should be restored and a point in time recovery should be done on thedatabase up to the time when the corruption could have occurred.

（8） truncate、drop是dll（data define language),操作立即生效，原数据不放到 rollback segment中，不能回滚。如果只是部分表格或者部分数据需要回滚，我们建议您通过创建临时实例来恢复数据，临时实例创建成功后从临时实例中把需要的数据导回到生产库。truncate、drop 是定义语言(ddl),操作立即生效，原数据不放到rollback segment中，不能回滚，操作不触发 trigger。

Current online Redo 和 Undo 损坏的处理方法

then copy the download shlwapi.dll to the folder, and clean the registry database of your system to repair the damaged or corrupted registry settings. commonly the related registry entries have been modified or damaged along with the corruption of shlwapi.dll file. you can do this work with a professional registry cleaner to scan the whole system first and then fix the problem. then restart your computer.。the initial segment size if the table is 5m. oracle database determines the size of each extent and the total number of extents allocated to satisfy the initial segment size. the segment's maximum size is limited to 100m.。if you are running the database in manual undo management mode, then at least one rollback segment other than the system rollback segment must be online.。

The supported way of fixing data dictionary corruption is to restore from a backupand roll forward using the archived redo logs.

4.3.4 Undo header and Undo blocks (ROLLBACK tablespace)

Rollback segments are undo segments that have information about the transaction that hasbeen executed so that it can be rolled back in case of failure of thetransaction or when the user asks for the transaction to be rolled backexplicitly.

They are made up of undo header blocks and undo blocks which are required to accessundo information to provide for consistent reads and transactionconsistency. If the rollback segment iscorrupted, the transaction consistency of the data blocks (including datadictionary objects) can be jeopardized.

The corruption found when undoing atransaction could fall under three categories ：

在以下三种情况下，可以会出现corruption：

（1）belongs to the object (table/index/cluster) that has the data onwhich the transaction was executed (data block)

（2）belongs to the undo block that is being used to undo the transaction(undo header)

' replaces or removes a header. if the header value is empty and the header is found,。 we found a string where it should not have been, overwriting part of a heap block header. this block is next to the one we are freeing, so the crash occurs when ntdll。oracle database always assigns an undo tablespace when you start up the database in automatic undo management mode. if no undo tablespace has been assigned to this instance, then the database uses the system rollback segment. you can avoid this by creating an undo tablespace, which the database will implicitly assign to the instance if no other undo tablespace is currently assigned.。

对于第一种情况，出现corruption 的位置是data block。

Thefirst case where the corruption is in the object to which the activetransaction belongs to, we have to identify the object first. This can be done by setting an event in theINIT.ORA as follows:

event= “10015 trace name context forever, level 10”

这种情况的坏块是active transaction，当我们重启DB后，会进行相关的transaction recover（Rolling Back）。 当recover 完成，就可以正常访问对应的block了。 相关文章参考：

还原真实的cache recovery

Oracle 实例恢复时 前滚（roll forward） 后滚（rollback） 问题

without flowers galvanized zinc plate zinc flower defect analysis by visiting this website information required in accordance with the number of charge information browsing fee, 0.01 yuan/article transaction serial number: order number: pc trading hours: address amount: 0.01 yuan payment bank...。提示e文：you should only run repair on damaged or corrupted databases. repair will not apply information in the transaction log files to the database and may cause information to be lost. do you wish to proceed。s solicitation of proxies for its special meeting of stockholders to vote on the proposed transaction because these documents will contain important information regarding the proposed transaction and related matters。

设置event时候，会dump DB 启动是的undo segment recovery，在trace里会有‘error recovering tx(#, #) object#’信息，其中Tx(#, #)指的是事务信息，object #是corruption 的对象id。找到对象ID 后可以通过如下SQL查询：

The following query gives the name of theobject that is corrupted:

SQL>SELECTOWNER, OBJECT_NAME, OBJECT_TYPE, STATUS FROM SYS.DBA_OBJECTS WHERE OBJECT_ID = <object #_from_tracefile>;

对于第二种情况和第三种情况的处理，参考我的blog：

Current online Redo 和 Undo 损坏的处理方法

4.3.5 Sort blocks (TEMP tablespace)

Sortsare usually done in the part of memory allocated from the SGA. This is defined by the INIT.ORA parameterSORT_AREA_SIZE. If the sort space neededfor a sort is so big that it cannot fit in the sort area defined in memory,then it is done on disk by creating segments called the Temporary segments.

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