RE: what could cause my oracle sequence nextval jump?

If you need secuential numbers and cannot afford either gaps or locking and generating numbers with a pl/sql function, you can always run a process on the affected tables and re-set the sequenced value in order to avoid gaps.

An alternative to sequences, when you cannot afford gaps is using custom pl/sql functions and perhaps even Oracle Queues. This would cause a serious serialization of operations though.

Guillermo Alan Bort
EDS - ITO DBA Main Group

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