Use the WITH ALLOCATION option to specify the number of pages initially allocated to the table or index. By pre-allocating disk space to a table, runtime errors that result from running out of disk space can be avoided. If the table is spread across multiple locations, space is allocated across all locations.

The number of pages specified must be between 4 and 8,388,607 (the maximum number of pages in a table). If the specified number of pages cannot be allocated, the modify statement is aborted.

A table can be modified to a smaller size. If the table requires more pages that you specify, the table is extended and no data is lost. A table can be modified to a larger size to reserve disk space for the table.

If not specified, a modify does not change a table's allocation.