# 2 vm.memory.size parameters

#### Overview

This section provides more details and platform-specific information on
the parameters of the `vm.memory.size[<mode>]` [agent
item](/manual/config/items/itemtypes/zabbix_agent).

#### Parameters

The following parameters are possible for this item:

-   **active** - memory currently in use or very recently used, and so
    it is in RAM
-   **anon** - memory not associated with a file (cannot be re-read from
    it)
-   **available** - available memory, calculated differently depending
    on the platform (see the table below)
-   **buffers** - cache for things like file system metadata
-   **cached** - cache for various things
-   **exec** - executable code, typically from a (program) file
-   **file** - cache for contents of recently accessed files
-   **free** - memory that is readily available to any entity requesting
    memory
-   **inactive** - memory that is marked as not used
-   **pavailable** - inactive + cached + free memory as percentage of
    'total'
-   **pinned** - same as 'wired'
-   **pused** - active + wired memory as percentage of 'total'
-   **shared** - memory that may be simultaneously accessed by multiple
    processes
-   **total** - total physical memory available
-   **used** - used memory, calculated differently depending on the
    platform (see the table below)
-   **wired** - memory that is marked to always stay in RAM. It is never
    moved to disk.

Platform-specific calculation of **available** and **used**:

|Platform|**"available"**|**"used"**|
|--------|---------------|----------|
|*AIX*|free + cached|real memory in use|
|*FreeBSD*|inactive + cached + free|active + wired + cached|
|*HP UX*|free|total - free|
|*Linux<3.14*|free + buffers + cached|total - free|
|*Linux 3.14+*|/proc/meminfo, "Cached":+"MemAvailable:"|total - free|
|*NetBSD*|inactive + execpages + file + free|total - free|
|*OpenBSD*|inactive + free + cached|active + wired|
|*OSX*|inactive + free|active + wired|
|*Solaris*|free|total - free|
|*Win32*|free|total - free|

::: noteimportant
The sum of *vm.memory.size\[used\]* and *vm.memory.size\[available\]* does not necessarily equal total. For instance, on FreeBSD:<br>
\* Active, inactive, wired, cached memories are considered used, because they store some useful information.<br>
\* At the same time inactive, cached, free memories are considered available, because these kinds of memories can be given instantly to processes that request more memory.

So inactive memory is both used and available simultaneously. Because of
this, the *vm.memory.size\[used\]* item is designed for informational
purposes only, while *vm.memory.size\[available\]* is designed to be
used in triggers.
:::

See the ["See also"](#see_also) section at the bottom of this page to
find more detailed information about memory calculation in different OS.

##### Platform-specific notes

-   on Linux **shared** works only on kernel 2.4

### See also

1.  [Detailed information about memory calculation in different
    OS](http://blog.zabbix.com/when-alexei-isnt-looking#vm.memory.size)