initial next minextents maxextents pctincrease

oracle initial next minextents maxextents pctincrease是什么意思？？？？？？？

INITIAL 100K NEXT 100K MINEXTENTS 1 MAXEXTENTS UNLIMITED PCTINCREASE 0

CREATE TABLESPACE WDK_CODE DATAFILE 'D:\ORADATA\CODE\CODE01.ora' SIZE 20M DEFAULT STORAGE ( INITIAL 100K NEXT 100K MINEXTENTS 1 MAXEXTENTS UNLIMITED PCTINCREASE 0 ) MINIMUM EXTENT 0K;
那位老兄能帮我解释一下上面的语句是什么意思？

 

 

create tablespace 语法

CREATE [UNDO] TABLESPACE tablespace
[DATAFILE datafile_tempfile_spec [, datafile_tempfile_spec]... ]
[{ MINIMUM EXTENT integer [ K | M ]
| BLOCKSIZE integer [K]
| logging_clause  
| FORCE LOGGING
| DEFAULT [data_segment_compression] storage_clause
| { ONLINE | OFFLINE }
| { PERMANENT | TEMPORARY }
| extent_management_clause
| segment_management_clause
}
[ MINIMUM EXTENT integer [ K | M ]
| BLOCKSIZE integer [K]
| logging_clause
| FORCE LOGGING
| DEFAULT [data_segment_compression] storage_clause
| { ONLINE | OFFLINE }
| { PERMANENT | TEMPORARY }
| extent_management_clause
| segment_management_clause
]...
]
;

 

 

 

 

 

INITIAL：specifies the size in bytes of the object's first extent.  Oracle allocates space for this extent when you create the object.  You can also use K or M to specify this size in kilobytes or megabytes.  The default value is the size of 5 data blocks.  The minimum value is the size of 2 data blocks.  The maximum value varies depending on your operating system.  Oracle rounds values up to the next multiple of the data block size.

NEXT：specifies the size in bytes of the next extent to be allocated to the object.  You can also use K or M to specify the size in kilobytes or megabytes.  The default value is the size of 5 data blocks.  The minimum value is the size of 1 data block.  The maximum value varies depending on your operating system.  Oracle rounds values up to the next multiple of the data block size.

MINEXTENTS：specifies the total number of extents allocated when the segment is created.  This parameter allows you to allocate a large amount of space when you create an object, even if the space available is not contiguous.  The default and minimum value is 1, meaning that Oracle only allocates the initial extent, except for rollback segments for which the default and minimum value is 2.  The maximum value varies depending on your operating system.
If the MINEXTENTS value is greater than 1, then Oracle calculates the size of subsequent extents based on the values of the INITIAL, NEXT, and PCTINCREASE parameters.

MAXEXTENTS：specifies the total number of extents, including the first, that Oracle can allocate for the object.  The minimum value is 1.  The default and maximum values vary depending your data block size.

PCTINCREASE：specifies the percent by which each extent after the second grows over the previous extent.  The default value is 50,  meaning that each subsequent extent is 50% larger than the preceding extent. The minimum value is 0, meaning all extents after the first are the same size.  The maximum value varies depending on your operating system.
You cannot specify PCTINCREASE for rollback segments.  Rollback segments always have a PCTINCREASE value of 0.
Oracle rounds the calculated size of each new extent up to the next multiple of the data block size.