f499a1c0_quences_in_Oracle__autonumber___Description
[Parameter] ORDER [Example] ORDER [Description] 
Specify ORDER to guarantee that sequence numbers are generated in order of request. You may want to use this clause if you are using the sequence numbers as timestamps. Guaranteeing order is usually not important for sequences used to generate primary keys. ORDER is necessary only to guarantee ordered generation if you are using Oracle with Real Application Clusters. If you are using exclusive mode, sequence numbers are always generated in order.
How to use sequences in Oracle (autonumber)
Description