Deferred extent storage allocation

If IN dbspace is the only storage specification for the new table, then by default 16 kilobytes of storage (or enough storage for four pages, if 4 pages require more than 16 kilobytes) are allocated for the first extent size at the time of table creation.

No storage is allocated for the first extent, however, if the CREATE TABLE statement includes none of the following storage specifications:
  • EXTENT SIZE
  • NEXT SIZE
  • IN dbspace.
In this case, storage allocation for the first extent is deferred until the first row is stored in the table.

The same storage allocation deferral applies to tables defined by the CREATE TEMP TABLE statement that do not include any of the storage specifications listed above.

When rows are first inserted into a table for which extent allocation has been deferred, the default size for the first extent is 16 kilobytes. If 16 kilobytes are insufficient for 4 pages, the first extent size will be 4 pages.

When reverting a Version 11.70 or later database server to an earlier release that does not support deferred extent allocation for empty tables, you must either drop or else insert a row into any empty database table that you wish to revert. Empty external tables that do not support INSERT operations must be dropped.