ITM Agent Insights: Calculating AIX OS agent memory attributes using AIX CLI

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This blog will give an example of how to determine the values returned in the memory attributes by the AIX OS agent through the AIX command line interface.

Below is an example which will explain the returned values:

# svmon -G
                   size          inuse           free           pin       virtual
memory    131072     120250       10822       73297   123145
pg space  131072     18088
 
Line "memory" refers to the RAM.
Line "pg space" is the paging space.

Column "size" is the total available amount of the given resource (memory/pg space).
Column "inuse" is the used amount of that resource (memory/pg space).
Column "free" is the available memory.
Column "pin" is the pinned memory. This memory cannot be paged out or moved.  

About the column "virtual", we must consider that the real memory consists of 2 parts:

1) the file cache, which is used to cache the files instead of writing them to the hard disk. This speeds up the file operations. This part gets written to the hard disk regularly.
2) the code and data pages created by the programs. This part is getting saved to the paging space when needed.
 
The column "virtual" shows the memory used by the second portion of the real memory mentioned above.

On AIX, the virtual memory is always the sum of RAM plus paging space which means that virtual memory is the sum of the values of line memory and line pg space.

All the values listed above are 4K blocks. So values of 131072 = 131072 x 4 = 524288 KBytes = 512 MBytes
 
Here are some examples:
a) Total Virtual Storage (MB):
Takes column size of lines memory and pg space:
131072 + 131072.
As these values are 4K pages:
131072 + 131072 = 262144 x 4 = 1048576 K = 1024 MB.
 

Total Virtual Storage (MB) = 1024 MB
 
b) Used Virtual Storage (MB):
Takes column inuse of lines memory and pg space:
120250 + 18088.
As these values are 4K pages:
120250 + 18088 = 138338 x 4 = 553352 K = 540.38 MB.
 
Used Virtual Storage (MB) = 540.38 MB
 
c) Total Swap Space (MB):
Takes column size of line pg space:
131072.
As this value is a 4K page:
131072 x 4 = 512 MBytes
 
There are no AIX commands available which really list the virtual memory, they always list the values for paging and / or RAM separately.

Additional ITM Agent Insights series of IBM Tivoli Monitoring Agent blogs are indexed under ITM Agent Insights: Introduction.

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