Using space management properties can increase the space needed for a table or an index. See “Effects of space management properties”, and “max_rows_per_page”.
The formulas in this section use the maximum size for variable-length character and binary data.To use the average size instead of the maximum size, see “Using average sizes for variable fields”.
If your table includes text or image datatypes or Java off-row columns, use 16 (the size of the text pointer that is stored in the row) in your calculations. Then see “LOB pages” to see how to calculate the storage space required for the actual text or image data.
Indexes on data-only-locked tables may be smaller than the formulas predict due to two factors:
Duplicate keys are stored only once, followed by a list of row IDs for the key.
Compression of keys on non-leaf levels; only enough of the key to differentiate from the neighboring keys is stored. This is especially effective in reducing the size when long character keys are used.
If the configuration parameter page utilization percent is set to less than 100, Adaptive Server may allocate new extents before filling all pages on the allocated extents. This does not change the number of pages used by an object, but leaves empty pages in the extents allocated to the object. See in the System Administration Guide.
