Re: >1 Virtual Shared Memory Segment slow down

David Williams wrote: > > I've been told by Informix that having >1 virtual shared memory > segment slows down your Informix Online Database server.[snip] > Why would added more shared memory segments slow down the server > (they are mapped contiguously but the way)?? > > Anything internal to any UNIX kernel which may affect performance? The person that told you this was most likely a bit confused. In *general*, there is no problem having more than 1 shared memory segment, virtual or otherwise. Of course, you don't want to have more shared memory allocated than you have physical memory, lest you suffer the ill-effects of a high level of paging. Most systems suffer no ill-effects having multiple segments. There does seem to be some small problem on HP systems. I don't have the details handy, but as I understand it, only the first few shared memory segments (I believe the number was 3) are actually cached, and any additional segments are kept swapped out until particular pages are needed. It has been a while since I first heard of this, and it may well have been addressed in later releases of HP/UX. -- Dave Kosenko, Informix Professional Services *********************************************** "I look back with some satisfaction on what an idiot I was when I was 25, but when I do that, I'm assuming I'm no longer an idiot." - Andy Rooney