Database Reference
In-Depth Information
The total amount of physical RAM used by a process is displayed in a column called
Working Set (Memory) .
A better column to watch if we want to monitor the physical RAM
consumed by a process is Memory (Private Working Set) , which is a
subset of the Working Set (Memory) counter that includes only the
data that cannot be shared with other processes. However, these two
numbers shouldn't be too different for Analysis Services.
The virtual memory manager in Windows is a complex system that aims to optimize
the usage of physical memory, sharing data between processes whenever it is
possible, but in general isolating each virtual address space from all the others in
a secure manner. For these reasons it is not easy to interpret the counters we just
mentioned, and it could be useful for you to recap how virtual memory allocation
works in Windows.
As we mentioned, data can be shared across different processes. For example, if
two different processes use the same DLL, the physical memory containing DLL
code is shared between both processes using read-only pages, regardless of the
virtual position of the code in each virtual address space. However, this feature
is not particularly important for Analysis Services because most of the memory is
consumed for data and it is private to the process. For this reason, for the rest of this
section we will concentrate on private memory and not on shared memory.
When a process allocates private memory, as Analysis Services does when it requires
space for its data, it is requested from virtual memory. When that memory is written,
the operating system ensures that the page is in physical RAM. When there is not
enough RAM to hold all the virtual memory pages used by running processes, the
operating system moves older pages from RAM to disk. These pages will be recalled
from disk as soon as a process needs to read or write data there. This activity is called
memory paging and we want it to happen as little as possible. One way to stop it
happening would be to remove the paging file from the operating system. This is
possible using the No paging file setting, but we do not recommend using this option
on a server that is running SQL Server or Analysis Services.
 
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