Sequence caching with toplink and oracle caching

Question

Hi,
In my application, I use toplink as a JPA provider. For performance reasons, I defined an allocationSize on sequence generator for some persistence objects. I read some documentation to understand how it works, the result of my research is that the allocationSize of sequence generator must match with the increment value of the sequence in database.
So if I want to cache 1000 of values, I must define on my sequence generator allocationSize of 1000 and create a sequence like this : create sequence myseq increment by 1000. Am I right ?
Second question, what if my sequence define a cache in the database. For example, create sequence myseq increment by 1000 cache 20.
Does it mean that 20 values will be cached or 1000*20 values will be cached ? Is the cache size defined per session or for all the sessions of the database ?
Thanks.
Will.

Answer 1

Thank you for your response.
I used the default parameter of toplink (increment by 50) and I left a cache size of 20 on database side.
But I noticed that whenever the server restarts, I "lost" between 900 and 1000 ids (nearly 20*50). So even if sequence cache on oracle size is non transactional, I think there is a kind of prefetch somewhere on the server side. I must not lost more than 50 ids when a server restarts.
If I remove the cache on database side, then the behavior is correct (the expected one to be more precise).
Is there any kind of sequence caching in oracle jdbc drivers ?
Thanks.
Will.