An unordered sequence is an integer (32-bit or 64-bit) sequence that returns non-consecutive values.

Unordered sequences are useful for applications that use the sequence to generate values for a B-tree indexed column. Because column values are generated in an unordered sequence, the B-tree can expand gracefully, without the overhead associated with continually adding entries at the end of the value range.

To request an unordered sequence, use the UNORDERED keyword on the CREATE SEQUENCE statement. Unordered sequences will produce all positive integer values before repeating.

For more information, see the SQL Reference Guide.