那是个很大的问题:
storage 是语法,表示下面是关与storage 的参数
initial 20K-->INITIAL specifies in bytes the size of the object's first extent. Oracle allocates space for this extent when you create the schema object. Use K or M to specify this size in kilobytes or megabytes. NEXT 20K-->NEXT specifies in bytes the size of the next extent to be allocated to the object. 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 depends on your operating system. Oracle rounds values up to the next multiple of the data block size for values less than 5 data blocks. For values greater than 5 data blocks, Oracle rounds up to a value that minimizes fragmentation. PCTINCREASE specifies the percent by which the third and subsequent extents grow over the preceding 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 depends on your operating system. Oracle rounds the calculated size of each new extent to the nearest multiple of the data block size. PATFREE -->let me think
storage 是语法,表示下面是关与storage 的参数
initial 20K-->INITIAL specifies in bytes the size of the object's first extent. Oracle allocates space for this extent when you create the schema object. Use K or M to specify this size in kilobytes or megabytes. NEXT 20K-->NEXT specifies in bytes the size of the next extent to be allocated to the object. 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 depends on your operating system. Oracle rounds values up to the next multiple of the data block size for values less than 5 data blocks. For values greater than 5 data blocks, Oracle rounds up to a value that minimizes fragmentation. PCTINCREASE specifies the percent by which the third and subsequent extents grow over the preceding 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 depends on your operating system. Oracle rounds the calculated size of each new extent to the nearest multiple of the data block size. PATFREE -->let me think
storage->指明的是指定建立该索引使用的存储分配参数
initial->指明index初始建立分配给多大的空间，这时是20k
next->指明的是，当该index需要扩展时，下一个区的大小
pctincrease->这一个extent相对上一个extent的增长量,下一个extent大小=上一个大小＊（1+pctincrease）
patfree->这个我没见过
PCTFREE defaults to 10% if not explicitly set.
initital：该索引段的初始大小
next：第一个增长的大小
pctincrease：以后每次增长增加的比例
patfree：应该是pctfree，块中保留用于update的空间