Zabbix Documentation 5.0

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manual:config:items:itemtypes:calculated

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manual:config:items:itemtypes:calculated [2016/10/25 05:35]
martins-v clarifying the meaning of 'parameter'
manual:config:items:itemtypes:calculated [2016/11/23 07:54]
martins-v removing auto numbering
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-==== - #7 Calculated items ====+==== 7 Calculated items ====
  
-=== Overview ===+=== Overview ===
  
 With calculated items you can create calculations on the basis of other items. With calculated items you can create calculations on the basis of other items.
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 To use calculated items, choose the item type **Calculated**. ​ To use calculated items, choose the item type **Calculated**. ​
  
-=== Configurable fields ===+=== Configurable fields ===
  
 The **key** is a unique item identifier (per host). You can create any key name using supported symbols. The **key** is a unique item identifier (per host). You can create any key name using supported symbols.
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 |**parameter(s)** |Function parameter(s),​ if required.| |**parameter(s)** |Function parameter(s),​ if required.|
  
-<note tip>All items that are referenced from the calculated item formula must exist and be collecting data. Also, if you change the item key of a referenced item, you have to manually update any formulas using that key.</​note>​+<note tip>All items that are referenced from the calculated item formula must exist and be collecting data (exceptions in [[:​manual/​appendix/​triggers/​functions#​functions_and_unsupported_items|functions and unsupported items]]). Also, if you change the item key of a referenced item, you have to manually update any formulas using that key.</​note>​
  
 <note important>​[[manual:​config:​macros:​usermacros|User macros]] in the formula will be expanded if used to reference a function parameter or a constant. User macros will NOT be expanded if referencing a function, host name, item key, item key parameter or operator.</​note>​ <note important>​[[manual:​config:​macros:​usermacros|User macros]] in the formula will be expanded if used to reference a function parameter or a constant. User macros will NOT be expanded if referencing a function, host name, item key, item key parameter or operator.</​note>​
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 Unlike trigger expressions,​ Zabbix processes calculated items according to the item update interval, not upon receiving a new value. Unlike trigger expressions,​ Zabbix processes calculated items according to the item update interval, not upon receiving a new value.
 +
 +<​note>​If the calculation result is a float value it will be trimmed to an integer if the calculated item type of information is //Numeric (unsigned)//​.</​note>​
  
 A calculated item may become unsupported in several cases: A calculated item may become unsupported in several cases:
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 Support for calculated items was introduced in Zabbix 1.8.1.\\ Starting from Zabbix 3.2 calculated items in some cases may involve unsupported items as described in [[:​manual/​appendix/​triggers/​functions#​functions_and_unsupported_items|functions and unsupported items]], [[:​manual/​config/​triggers/​expression#​expressions_with_unsupported_items_and_unknown_values|Expressions with unsupported items and unknown values]] and [[:​manual/​config/​triggers/​expression#​operators|Operators]]. Support for calculated items was introduced in Zabbix 1.8.1.\\ Starting from Zabbix 3.2 calculated items in some cases may involve unsupported items as described in [[:​manual/​appendix/​triggers/​functions#​functions_and_unsupported_items|functions and unsupported items]], [[:​manual/​config/​triggers/​expression#​expressions_with_unsupported_items_and_unknown_values|Expressions with unsupported items and unknown values]] and [[:​manual/​config/​triggers/​expression#​operators|Operators]].
-=== Usage examples ===+ 
 +=== Usage examples ===
  
 == Example 1 == == Example 1 ==