If the disk space allocated for
a next extent is physically contiguous with disk space already allocated
to the same table, the database server allocates the disk space but
does not consider the new allocation as a separate extent. Instead,
the database server extends the size of the existing contiguous extent.
Thereafter, all disk-space reports reflect the allocation as an extension
of the existing extent. That is, the number of extents reported is
always the number of physically distinct extents, not the number of
times a next extent has been allocated plus one (the initial extent). Next-Extent
Allocation Strategies illustrates extent-allocation
strategies. Figure 1: Next-Extent
Allocation Strategies
After disk space is allocated to a tblspace as part of
an extent, the space remains dedicated to that tblspace even if the
data contained in it is deleted. For alternative methods of reclaiming
this empty disk space, see your Informix® Performance Guide.
