As promised I will keep you up to date about the problem in my previous post about the issues with ASM on Solaris when a large amount of files exists (or have existed). I can confirm that there is a fix now that completely solves the problem.
The solution consists of patch 6270137, which prevents the blocking effect of asm when scanning through the files. Support recommends installing as well patch 6264570, but I can’t confirm that this one is really necessary (I don’t think so).
Anyway, I must congratulate Oracle Support for their strong effert and quick solution of the problem (the patch is already out since 18 Mar, this blog article about it comes much later).