Memory is a resource from the memory pool that the subsystem uses to run the job. The amount of memory in a memory pool, as well as how many other jobs are competing for memory, affect how efficiently a job runs.
Memory pools provide jobs with memory in which to run. Many factors affect how the job runs in the memory pool, such as the size of the memory pool, the activity level in the memory pool, and paging and faulting. The activity level in memory pools directly relates to the number of threads that are allowed to run in the memory pool at one time. Remember, every job has at least one active thread, but some can have multiple threads. Threads give a job the ability to do more than one thing at a time. For example, one thread can go out and do calculations while another thread waits for more data to process.
Paging is the movement of data in and out of memory, both synchronously and asynchronously. Pages can be written out to storage or removed from memory without being written if they have not been changed. Faulting causes paging to occur on the server. Faulting occurs when a referenced page, or piece of data, is not in memory. This causes programs to stop because they must wait for the data to be paged in.
Subsystems use different memory pools to support different types of jobs that run within them.