Home » Infrastructure » Linux » Why would Oracle use swap space when it has 32 GB RAM (Oracle 11g, RHEL)
Why would Oracle use swap space when it has 32 GB RAM [message #307370] Tue, 18 March 2008 11:31 Go to next message
Messages: 6
Registered: March 2008
Junior Member
We have a 64-bit system running on RHEL and Oracle 11g. Using the new Automatic Memory Management feature, the MEMORY_TARGET was set 30 GB.

THe RAM is 32 GB, and the swap space is 2GB (The LInux/Oracle install guide recommended that over 8GB RAM, use 0.75 of RAM size for the swap space, but somehow that was our settings because it was believed that Oracle would not need the swap since it has been allocated so much RAM. )

We ran an data Load process - direct path insert, parallel 32, no logging.

$ top shows that the 2GB swap space was all used up.

When we then changed MEMORY_TARGET = 28 GB, again 2GB swap
space was all used up.

In both cases, the whole system frozed up, and we had to hard reset the LInux box.

Question 1 :

Why would oracle use the swap memory when it was allocated so much space, ie 30GB ?

By the way, the same load process runs fine on another system with 8GB RAM and MEMORY_TARGET set to just 3.7 GB.

Question 2 :

How do we tell if Oracle is using the swap spaces ? And how do we tell how much swap space it was using ?

Question 3 :

Mem: 32939884k total, 16952048k used, 15987836k free, 1437924k buffers
Swap: 2096376k total, 2093700k used, 2676k free, 13969188k cached

What does the "13969188k cached" mean ?

And why swap is being "2093700k used" when RAM has "15987836k free" ? Isn't swap only utilized when there is little or no RAM left ?

Thank you very much for your comments and feedback.

Re: Why would Oracle use swap space when it has 32 GB RAM [message #307373 is a reply to message #307370] Tue, 18 March 2008 11:48 Go to previous message
Messages: 24958
Registered: January 2009
Location: SoCal
Senior Member
sar -r will show memory & swap usage at the sar snapshot intervals

I suggest you follow Oracle recommendations WRT swap size & increase it.

After you determine how much swap space is needed then reduce SGA_TARGET so that 0 swap usage is achieved.
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