database - How oracle sequence works internally? -

i wan know how sequence table works internally in oracle database. specially how increment value of sequence.

are use trigger incrementing value of sequence or else???

oracle not handle sequences other objects, tables. if insert 100 records using nextval , issue rollback, sequence not rolled back. instead, 100 records have incremented sequence. next insert have 101-st value of sequence. lead "spaces" in sequence. allows multiple people safely use sequences without risk of duplicates. if 2 users simultaneously grab nextval, assigned unique numbers. oracle caches sequences in memory. init.ora parameter sequence_cache_entries defines cache size.