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1 Reply Latest reply: Oct 31, 2012 11:44 AM by user12273962 RSS

Linux guest o/s not at all using swap, on Oracle VM Server

User378152 Newbie
Currently Being Moderated
Hi,
I've created 4 VMs with OEL 5.6 x64 o/s for setting up a 11g RAC environment.

all the 4 vms are assigned with 8gig of SWAP space and 5Gig of memory. The guest o/s installation and configurations are just went fine.

While configuring the database, I observed that the guest o/s is not at all using the swap space.

Even though, the physical memory is used more than 80%, not even 1% of swap is used by the guest VM. This phenamenon is same across all the 4VMs.

Here's the output of top command:
top - 21:32:21 up 2:15, 4 users, load average: 0.00, 0.00, 0.00
Tasks: 133 total, 2 running, 131 sleeping, 0 stopped, 0 zombie
Cpu(s): 0.0%us, 0.3%sy, 0.0%ni, 99.3%id, 0.3%wa, 0.0%hi, 0.0%si, 0.0%st
Mem: 5058928k total, 4355808k used, 703120k free, 185676k buffers
Swap: 8289532k total, 0k used, 8289532k free, 2306880k cached

Is it necessary to configure swap on Oracle Virtual Server Guests ?
  • 1. Re: Linux guest o/s not at all using swap, on Oracle VM Server
    user12273962 Pro
    Currently Being Moderated
    This how Linux works. It has nothing to do with Oracle VM.

    Why in the world would you want your VM guest to actively use a swap file? One of the greatest assets to any linux environment is linux will not use a page file unless it is absolutely necessary. If you have an oracle database actively forcing writes to a swap file... .then reduce your overall memory allocation to the database.

    I'd just as soon read the block from disk again instead of swaping it out a page file.

    Are you dedicating a disk or disks to just handle "swapping"? If not, then realize all of it is coming out of the same io path.

    Yes. You must specify a page file with a Oracle Database. I don't even use the minimum required and ignore the error message on the prereq check. Also, if for some reason you do run out of physical memory.... linux will crash if no swap file is used. However, if you have something causing paging..... In my opinion you should check into it.

    Edited by: user12273962 on Oct 31, 2012 11:37 AM

    Edited by: user12273962 on Oct 31, 2012 11:42 AM

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