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# 1 vm.memory.size parameters

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#### Overview

This section provides some parameter details for the [vm.memory.size\[<mode>\]](/manual/config/items/itemtypes/zabbix_agent#vm.memory.size) agent item.

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#### Parameters

The following parameters are available 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** - 'available' memory as percentage of 'total'
    (calculated as `available`/`total`\*100)
-   **pinned** - same as 'wired'
-   **pused** - 'used' memory as percentage of 'total' (calculated as
    `used`/`total`\*100)
-   **shared** - memory that may be simultaneously accessed by multiple
    processes
-   **slab** - total amount of memory used by the kernel to cache data
    structures for its own use
-   **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.

::: notewarning
Some of these parameters are platform-specific and
might not be available on your platform. See [Zabbix agent items](/manual/config/items/itemtypes/zabbix_agent) for
details.
:::

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+*<br>(also backported to 3.10 on RHEL 7)|/proc/meminfo, see "MemAvailable" in Linux kernel [documentation](https://www.kernel.org/doc/Documentation/filesystems/proc.txt) for details.<br>Note that free + buffers + cached is no longer equal to 'available' due to not all the page cache can be freed and low watermark being used in calculation.|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.
:::

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### See also

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

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