Shulou(Shulou.com)06/01 Report--

Demand:

It is necessary to sort out the tablespaces created by on-site users and their stored data for standardized management. When sorting out the tablespaces created by the user site, you need to exclude non-user-created tablespaces, all of which first need to be user-created and those that come with Oracle.

The local test builds a new library and finds that the table space comes with the following:

The following is a brief description of each tablespace (part of the content is quoted from the network):

1. SYSAUX tablespace

SYSAUX table space is introduced in Oracle Database 10g as an auxiliary table space of SYSTEM table space. Some database components that used to use independent tablespaces or system tablespaces are now created in SYSAUX tablespaces. SYSAUX tablespaces store some other metadata components, such as OEM,Streams, which are stored in SYSAUX tablespaces by default. By separating these components and functions, the load on SYSTEM tablespaces is reduced. The fragmentation of SYSTEM tablespaces caused by repeated creation of related objects and components can be avoided.

2. SYSTEM tablespace

SYSTEM tablespaces are created automatically by Oracle when creating databases. Every Oracle database will have SYSTEM tablespaces, and SYSTEM tablespaces should always be kept in online mode because they contain the basic information required by the database operation, such as: data dictionary, online help mechanism, all fallback segments, temporary periods and bootstrap segments, all user database entities, tables required by other ORACLE software products, and so on.

3. TEMP tablespace

Temporary tablespaces are used to manage database sorting operations and to store temporary objects such as temporary tables and intermediate sorting results. When SORT is needed in ORACLE, and when the size of sort_area_size in PGA is not enough, the data will be sorted in temporary tablespaces. Temporary tablespaces may be used for operations like CREATE INDEX, ANALYZE, SELECT DISTINCT, ORDER BY, GROUP BY, UNION ALL, INTERSECT, MINUS, SORT-MERGE JOINS, HASH JOIN, and so on. When the operation is completed, the system will automatically clean up the temporary objects in the temporary tablespace and automatically release the temporary segment. The release here is only marked as idle and can be reused, but the actual disk space is not really released. This is why temporary tablespaces sometimes grow. Temporary tablespaces store the intermediate results of large-scale sorting operations (small-scale sorting operations are done directly in RAM, large-scale sorting requires disk sorting Disk Sort) and hash operations. It differs from permanent tablespaces in that it consists of temporary data files (temporary files) rather than permanent data files (datafiles). Temporary tablespaces do not store objects of permanent type, so it does not and does not need to be backed up. In addition, operations on temporary data files do not generate redo logs, but undo logs are generated.

4. UNDO tablespace

UNDO tablespaces are a concept unique to Oracle. Undo segments are automatically allocated in the undo table space, and these undo segments are used to hold the undo information of the DML statement in the transaction, that is, to hold the value of the data before it was modified. In rollback, instance recovery (roll forward), consistency reads the construction of CR blocks using undo information. Due to the introduction of undo, the select statement of Oracle does not need any locks to achieve consistent reading. There are many similarities between undo tablespaces and other tablespaces: undo blocks are also read and cached by buffer cache, redo log is generated when modified, and data is written back to disk in undo tablespaces. So after the crash, the buffer cache of the undo block will also recover.

5. USERS tablespace

The creation user must specify a tablespace for it, or if the default tablespace is not explicitly specified, it is specified as a users tablespace, and all information about this user is put into the users tablespace.

Summary

The above is the detailed description of the table space in the Oracle database introduced by the editor. I hope it will be helpful to you. If you have any questions, please leave a message for me, and the editor will reply to you in time. Thank you very much for your support to the website!

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