ORACLE表空间bigfile和smallfile
Use this clause to determine whether the tablespace is a bigfile or smallfile tablespace. This clause overrides any default tablespace type setting for the database.
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A bigfile tablespace contains only one data file or temp file, which can contain up to approximately 4 billion (232) blocks. The maximum size of the single data file or temp file is 128 terabytes (TB) for a tablespace with 32K blocks and 32TB for a tablespace with 8K blocks.
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A smallfile tablespace is a traditional Oracle tablespace, which can contain 1022 data files or temp files, each of which can contain up to approximately 4 million (222) blocks.(default)
If you omit this clause, then Oracle Database uses the current default tablespace type of permanent or temporary tablespace set for the database. If you specify BIGFILE for a permanent tablespace, then the database by default creates a locally managed tablespace with automatic segment-space management.
Restriction on Bigfile Tablespaces You can specify only one data file in the DATAFILE clause or one temp file in the TEMPFILE clause.
Bigfile Tablespaces
A bigfile tablespace is a tablespace with a single, but potentially very large (up to 4G blocks) data file. Traditional smallfile tablespaces, in contrast, can contain multiple data files, but the files cannot be as large. The benefits of bigfile tablespaces are the following:
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A bigfile tablespace with 8K blocks can contain a 32 terabyte data file. A bigfile tablespace with 32K blocks can contain a 128 terabyte data file. The maximum number of data files in an Oracle Database is limited (usually to 64K files). Therefore, bigfile tablespaces can significantly enhance the storage capacity of an Oracle Database.
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Bigfile tablespaces can reduce the number of data files needed for a database. An additional benefit is that the
DB_FILESinitialization parameter andMAXDATAFILESparameter of theCREATE DATABASEandCREATE CONTROLFILEstatements can be adjusted to reduce the amount of SGA space required for data file information and the size of the control file. -
Bigfile tablespaces simplify database management by providing data file transparency. SQL syntax for the
ALTERTABLESPACEstatement lets you perform operations on tablespaces, rather than the underlying individual data files.
Bigfile tablespaces are supported only for locally managed tablespaces with automatic segment space management, with three exceptions: locally managed undo tablespaces, temporary tablespaces, and the SYSTEM tablespace.
Notes:
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Bigfile tablespaces are intended to be used with Automatic Storage Management (Oracle ASM) or other logical volume managers that supports striping or RAID, and dynamically extensible logical volumes.
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Avoid creating bigfile tablespaces on a system that does not support striping because of negative implications for parallel query execution and RMAN backup parallelization.
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Using bigfile tablespaces on platforms that do not support large file sizes is not recommended and can limit tablespace capacity. See your operating system specific documentation for information about maximum supported file sizes.
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Creating a Bigfile Tablespace
To create a bigfile tablespace, specify the
BIGFILEkeyword of theCREATETABLESPACEstatement (CREATEBIGFILETABLESPACE...). Oracle Database automatically creates a locally managed tablespace with automatic segment space management. You can, but need not, specifyEXTENTMANAGEMENTLOCALandSEGMENTSPACEMANAGEMENTAUTOin this statement. However, the database returns an error if you specifyEXTENTMANAGEMENTDICTIONARYorSEGMENTSPACEMANAGEMENTMANUAL. The remaining syntax of the statement is the same as for theCREATE TABLESPACEstatement, but you can only specify one data file. For example:CREATE BIGFILE TABLESPACE bigtbs DATAFILE ‘/u02/oracle/data/bigtbs01.dbf‘ SIZE 50G ...You can specify
SIZEin kilobytes (K), megabytes (M), gigabytes (G), or terabytes (T).If the default tablespace type was set to
BIGFILEat database creation, you need not specify the keywordBIGFILEin theCREATE TABLESPACEstatement. A bigfile tablespace is created by default.If the default tablespace type was set to
BIGFILEat database creation, but you want to create a traditional (smallfile) tablespace, then specify aCREATESMALLFILETABLESPACEstatement to override the default tablespace type for the tablespace that you are creating.
Identifying a Bigfile Tablespace
The following views contain a BIGFILE column that identifies a tablespace as a bigfile tablespace:
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DBA_TABLESPACES -
USER_TABLESPACES -
V$TABLESPACE
You can also identify a bigfile tablespace by the relative file number of its single data file. That number is 1024 on most platforms, but 4096 on OS/390.
原文：http://www.cnblogs.com/rusking/p/4285658.html