Impressum

Responsible for content:

Peter Ramm 
Hauptstraße 18 
D-01737 Oberhermsdorf 
Germany 

Email: Peter@ramm-oberhermsdorf.de

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Common pitfalls using SQL*Net via Firewalls

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Oracle-DB: How to check for appropriate sequence caching

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A common pitfall while using sequences in Oracle-DB is forgetting to define sequence caching. The default for sequences is cache size = 0. That means, every sequence.nextval operation triggers a single write operation on dictionary table sys.SEQ$. Especially if frequently calling sequence.nextval uncached sequences may cause significant performance degradation. Frequently calling sequence.nextval in parallel sessions may lead to ramdom lock scenarios in library cache. Setting a cache size for a sequence may heavy increase performance of nextval-operations. There's a minimal memory overhead for caching a sequence because all that's needed is a counter to increase in SGA memory and a upper limit. If this limit is reached with the counter, the upper limit is increased by cache size and the new upper limit is written down once to SEQ$. The possible drawback for sequence caching is that you loose all your values between the current value and the highest cached value if yo
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Oracle-DB: Link between audit trail and active session history

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