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I get that Paging Space in AIX is actually like SWAP in Linux. In one of my AIX servers at work, i'm actually seeing 99.7% Physical memory being utilized when my application is running(handling quite some data). Most of the time Server is utilizing 95% of Physical memory(RAM). From the pic attached, we can see Paging Space is being utilized. And i believe my Application can run little faster if i upgrade RAM.

But i am not able to convince the management. They say that still Paging Space is there and until it's utilized fully, no need to upgrade RAM.

enter image description here

Isn't paging Space actually in Hard Disk ?

OS actually transfer data between Paging Space(Hard Disk) & RAM back & forth in case of High Memory Utilization ?

Can someone please shed light that if i am using up 99.7% of Physical Memory - RAM in Server,it's a Good reason to upgrade RAM ?

Note: I'm posting here as a last resort and in need of proof to convince my management to upgrade the RAM in my server before Christmas, as i will be seeing quite a lot of data during Christmas. So Please, before down-voting, at least help me what's wrong with my question and help me get an answer.

  • I don't know about AIX, but in general I'd expect the OS to be using near all available RAM. Why have a resource and not use it for something? The question is really, when RAM is needed, can consumers get it? For example, if some of the RAM is being used for in-kernel buffers, can those buffers be flushed and the memory be reallocated to something else? In terms of the paging space in use, that's really more of a question of "how often are pages being written to/read from disk from/to memory? If that's something that's happening frequently, that'd be a sign that you might need more RAM. – Andy Dalton Dec 5 '17 at 20:07
  • What's the resident set size of your program? Does it do lots of file io, that is, are the file io numbers in your screendump due mostly to your program? – Mark Plotnick Dec 5 '17 at 22:38
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Yes, I would think that 'Page Space' is referring to virtual memory, which is analogous to Swap space in Linux. This page/swap space is indeed stored on the hard disk. Copying data to/from the hard disk takes longer than copying it into/out of RAM.

In the ideal situation, there would be infinite RAM and so no need for any page space at all. Therefore, it seems reasonable to conclude that, if your system is having to use 35% of your page space, because there is no more RAM available, then there will be some performance overhead, due to the hard disk read/writes.

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maybe it will help you The management of memory pages in RAM or on disk is handled by the Virtual Memory Manager (VMM). Virtual-memory segments are partitioned in units called pages. A paging space is a type of logical volume with allocated disk space that stores information which is resident in virtual memory but is not currently being accessed. This logical volume has an attribute type equal to paging, and is usually simply referred to as paging space or swap space. When the amount of free RAM in the system is low, programs or data that have not been used recently are moved from memory to paging space to release memory for other activities.

https://www.ibm.com/support/knowledgecenter/en/ssw_aix_61/com.ibm.aix.osdevice/pg_space_vm.htm

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  • Was there supposed to be something in the quote box there? – Time4Tea Dec 5 '17 at 19:33
  • @Jose So just asking the obvious, would it help if i increase the RAM in the Server ? – Bruce Dec 5 '17 at 19:43
  • Yes, you really need more RAM , :) – Jose Finger Dec 5 '17 at 19:48
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That memory is fully used is a "good thing". Memory is designed to be used.

Memory could be reported "in use" by processes that were loaded before but (as memory was not needed for some other job) not yet freed. If some process load a "lot of data" in a short time, this is more probable. But that memory would not be freed (even if the process is not using such data) until some other process takes precedence. Use memory with more frugality.

That there is a 35.5% of 20000 MB of PageSpace in use means that about ~7GB of data in disk that could have been in memory if it were available. Having ~24GB (24576 MB) of memory already installed means that only a 35% of memory has been paged. That may be solved by optimizing your data processing. Maybe loading smaller blocks of data at once.

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