Extent size
The default size for first and next extents is 16 kilobytes. If this translates to fewer than 4 pages in a particular dbspace, the database server uses the minimum extent size of 4 pages. For example if a dbspace has a page size of 8 kilobytes, 16 kilobytes is only 2 pages, so the database server increases the extent size to 32 kilobytes.
The maximum configurable size of an extent (EXTENT SIZE, NEXT SIZE) is 16,777,215 pages. As a table is loaded, however, extent concatenation may result in much larger extents.
If the chunk is smaller than the maximum size, the maximum extent size depends on the contiguous space available in the chunk.
Tblspaces that hold index fragments follow different rules for extent size. The database server bases the extent size for these tblspaces on the extent size for the corresponding table fragment. The database server uses the ratio of the row size to index key size to assign an appropriate extent size for the index tblspace (see the sections on estimating index page size and fragmenting table indexes in the HCL® Informix® Performance Guide).
The maximum number of extents for a partition is 32767.