We are using Hibernate 4.0.0 version with Oracle 12c database and we are using Sequence Generation for our ids. But the sequence generator is not generating the ids in continuous order. It is generating in random order. Due to this we have to increase column length from 3 to 5.

@Id
@Column(name = C_XXXXX)
@SequenceGenerator(name = SEQUENCE_XXX, sequenceName = SEQUENCE_XXX)
@GeneratedValue(strategy = GenerationType.SEQUENCE, generator = SEQUENCE_XXX)
private long someId;


Our Sequence Parameters:
MIN_VALUE 1
MAX_VALUE 99999999
INCREMENT_BY 1
CYCLE_FLAG N
ORDER_FLAG N
CACHE_SIZE 20
LAST_NUMBER 81
PARTITION_COUNT
SESSION_FLAG N
KEEP_VALUE N

The database sequence is a non-transactional sequence generator, so values are not guaranteed to be consecutive because one transaction might just roll back a given SQL INSERT.

The only requirement is that sequences need to be monotonically increasing, and that's how it should work. So, the values are not assigned randomly at all. It's just that gaps are not an issue at all.