The Vertica Database Forums

Is there any reason why different system tables should give different numbers for memory usage?

The docs (I'm using Vertica 7.1.X) say to look at RESOURCE_ACQUISITIONS.MEMORY_INUSE_KB and subtract QUERY_PROFILES.RESERVED_EXTRA_MEMORY to get "the memory in use".

That gives a very different number than SYSTEM_RESOURCE_USAGE.average_memory_usage_percent. (My impression is that this number will show lower memory usage than the previous one, at least in the example I'm looking at.) They're the same order of magnitude, but certainly not within a small error of each other.

I realize that there are good reasons why these could be different, but I don't know any details.

“resources acquired” is memory that is reserved within the resource pool. There is no guarantee that the memory will actually be used.

“memory usage” is memory that is actually allocated from the OS.

There’s some discussion of the difference here:

https://community.vertica.com/vertica/t ... mory_usage

—Sharon