13.4 Sequences

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Sequences can be cached. Twenty sequences are cached by default. If a system failure occurs then all cached sequences are lost.

Tip 

Only sequence numbers are lost if a database server crashes, not log file recoverable rows in tables, or any other operations using sequence values.

If required by local law that all sequence numbers added to something like invoices must exist then always create sequences with the NOCACHE option. Generally extensive sequence caching is useful for highly active concurrent OLTP or Oracle RAC installations. I have never seen extensive caching of sequences adversely affect performance except in circumstances where sequences were abused.

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