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I need to know what is the actual effect of Swap memory full ?. I have already enough ram but it is still using swap memory? I am using Server With Oracle 11g Database. So if because of swap memory full does it make an effect on the database? Current Scenario if server memory usage

free -h
         total        used        free      shared  buff/cache   available
Mem:       31G         10G        176M         17G         20G        2.9G
Swap:     2.0G        2.0G        152K
  • Some application had used a lot of ram. And no application requires that pages from swap til now. – Ipor Sircer Jul 31 '18 at 10:23
  • What is effect of High Swap Usage ? – vvs Jul 31 '18 at 10:29
  • more free memory. – Ipor Sircer Jul 31 '18 at 10:31
  • sorry ? i can't get it – vvs Jul 31 '18 at 10:38
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Take a look at this link. Here your system has a free RAM , approximately 3GB. But the system is still using swap space.

  1. The system can do a swap in/out from the swap space as and when required.
  2. But if there are many swap in/out operations i.e many disk operations, eventually this will effect the performance of applications. With aggressive swapping the effect on your database could be that the Query takes longer to fetch the results.There could be an overall impact on the system performance.
  3. Just to get a fair bit of idea of how your system is functioning, run the sar -B command and observe the column %vmeff:

%vmeff Calculated as pgsteal / pgscan, this is a metric of the efficiency of page reclaim. If it is near 100% then almost every page coming off the tail of the inactive list is being reaped. If it gets too low (e.g. less than 30%) then the virtual memory is having some difficulty. This field is displayed as zero if no pages have been scanned during the interval of time.

The sample output of sar -B 1:

05:12:13 PM  pgpgin/s pgpgout/s   fault/s  majflt/s  pgfree/s pgscank/s pgscand/s pgsteal/s    %vmeff
05:12:14 PM      0.00    294.95     33.33      0.00    313.13      0.00      0.00      0.00      0.00
05:12:15 PM      8.00    377.00     35.00      0.00    433.00      0.00      0.00      0.00      0.00

EDIT:

Checkout this link for the procedure to add swap space.

  • Ok @sai sasanka for the replay , Now i understood very well and i think i need to make a free swap memory . is it risky to free swap memory on live ? – vvs Jul 31 '18 at 13:10
  • @vvs, check the edited answer it has the procedure to increase the swap size. – sai sasanka Aug 1 '18 at 5:18
  • @vvs I must say that I didn't get to try the procedure since I didn't have a Ubuntu machine available. – sai sasanka Aug 1 '18 at 6:36

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