Oracle Core: Essential Internals for DBAs and Developers

Sequences

I’ll spend the rest of this chapter on a more concrete example of the problems you can run into, and the way you have to look at RAC, by picking a single, simple piece of functionality and examining the anomalies that start to appear when RAC gets thrown into the equation. There’s no specific reason why I picked sequences as the focus of this section—they just happen to offer an easy way of producing results that make the type of generic points I want to raise. We’ll start by clearing up a couple of common misconceptions about sequences, then examine the way that the internal implementation of sequences is subject to a couple of problems in RAC, then we’ll see how one of the commonest methods of using sequences needs to be reconsidered ...