Odd Bufferpool Behaviou

AIX 6.1 IDS 11.70.FC8X8 I have a new machine with a lot of extra memory. Given that, I added a bunch of new buffers (4k, 8k, & 16k) and went to town testing away. Long story short, with all those new buffers, I get virtual segments added at startup. In onstat -g mem, I see some very large pools named orvfl-buff(number). When Ireduce number of buffers to original settings, those guys go away. Has anyone seen this behavior before? Does it negatively impact performance? I plan to find the sweet spot with the largest number of buffers and no extras in the virtual portion but cannot do that today. Thanx, Dan

Original post: AIX 6.1 IDS 11.70.FC8X8 I have a new machine with a lot of extra memory. Given that, I added a bunch of new buffers (4k, 8k, & 16k) and went to town testing away. Long story short, with all those new buffers, I get virtual segments added at startup. In onstat -g mem, I see some very large pools named orvfl-buff(number). When Ireduce number of buffers to original settings, those guys go away. Has anyone seen this behavior before? Does it negatively impact performance? I plan to find the sweet spot with the largest number of buffers and no extras in the virtual portion but cannot do that today. Thanx, Dan Response: In 11.70 if you have either enough different bufferpools or 1 specific big enough buffer pool (such that you exhaust the max size for 1 segment, specifically the 1 resident segment), then the bufferpools spill over into additionally created virtual segments, and a orvfl_buff pool gets created to put the buffer pool into that virtual memory (since it's no longer in the resident segment). So what you are seeing is expected in 11.70. In 12.x the buffer pool code was changed (in whatever version where buffer pools became dynamic) so that each buffer pool would then attempt to create it's own shared memory segment (which was now of type "B" rather then resident or virtual segments). The buffer pool in virtual segments should not impact performance, assuming you have the physical memory on the machine to backup the amount of total shared memory being created. Jacques Renaut IBM Informix Advanced Support APD Team