I was approached that in one of the system, there was an alert displaying in the custom dashboard
saying that there was low memory free available in the CS (ASCS01 server (distributed production
Since the CS (Central Service System) ASCS01 contains only two services : message service and
Enqueue service; there will be never much RAM memory utilization takes place.
Hence decided to investigate whether there was indeed almost 98% RAM memory utilization takes
place ? The explanation and procedure is described below
As it is only ASCS system i.e. Central Service system where enqueue and message services
installed, total RAM memory capacity = 4GB is sufficient.
As shown in the above, out of total Physical RAM memory 4211792K, 4085616K is used i.e. almost
98% utilized. That means it looks like less memory available but actually not. The reason is given
Execute “Free -m” command at root level as shown in the figure below
Memory 2570M (i.e. 2.5GB) is actually free and 1542 Mb i.e. 1.5GB is used by application.
The reason is that out of the total amount of available memory is 4113M (i.e. 4GB), 1542M are used
by processes and 2570 Mb are free.
Linux is borrowing unused memory for disk caching. This makes it looks like that there is low on
memory, but really it is not ! Everything is fine!
Disk caching makes the system much faster! It does not take memory away from applications in any
If your applications want more memory, then disk cache can always be given back to applications
immediately! Thus there is no low on RAM.
If more memory is needed by programs , then Linux will free up the buffers and cache to yield
memory for the applications.
When an application processes not requires any more memory , then unused memory will return
back to Filesystems or disk cache.
As per Linux memory Architecture, 90% of Unused free RAM goes to Buffers / Disk Cache /
This is applicable for all systems including standalone Database system or CI+CS+DB etc.
Despite showing 98% memory utilization; actual memory utilization as shown in the command Free
-m (second line in “used” column) is less utilized and has more memory available as shown
in the “free” column of second line.
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